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Expanding bullet
An expanding bullet, also called a dum-dum bullet, is a projectile that deforms on impact to transfer more energy, banned in war but standard for hunting and policing.
Expanding Polytope Algorithm
The Expanding Polytope Algorithm (EPA) is an iterative computational geometry algorithm, devised by Gino van den Bergen, that computes penetration depth and contact normal between two intersecting convex shapes.
Expanse (supercomputer)
Expanse is a petascale supercomputer at the San Diego Supercomputer Center at UC San Diego, funded by the National Science Foundation and in production since December 2020.
Expansion card
An expansion card, also called an expansion board or add-in card, is a circuit board inserted into a motherboard to add functions like graphics or networking.
Expansion chamber
An expansion chamber is the tuned, trumpet-then-funnel exhaust of two-stroke engines, using pressure waves to scavenge the cylinder and raise power by up to 15 to 20 percent.
Expansion joint
An expansion joint, also called a movement joint, is a deliberate gap or flexible bellows that lets bridges, buildings, and pipelines expand and contract without cracking.
Expansion of Gatwick Airport
The Expansion of Gatwick Airport, known as the Northern Runway Project, is a £2.2 billion plan approved in 2025 to bring Gatwick's northern standby runway into routine use from 2030.
Expansion ratio (engine)
The expansion ratio of a piston engine is the ratio of cylinder volume at the end of the power stroke to the volume at the start of expansion.
Expect
Expect is a Tcl extension and standalone interpreter for automating interactive programs such as telnet, ftp, and passwd, conceived by Don Libes at NIST in 1987 and released in 1990 as public domain.
Expectation propagation detection
Expectation propagation detection (EPD) is an iterative approximate Bayesian method for recovering transmitted symbols in MIMO wireless receivers, reaching near maximum-likelihood accuracy at polynomial computational cost.
Expected calibration error
Expected calibration error (ECE) is a widely used machine learning metric, introduced at Cornell in 2017, that measures the gap between a model's stated confidence and its actual accuracy.
Expected improvement
Expected improvement (EI) is an acquisition function in Bayesian optimization that picks the next evaluation where the expected gain over the best value so far is largest.
Expedia
Expedia, also known as Expedia.com, is an American online travel agency and technology company launched by Microsoft in 1996, now one of the world's largest travel booking platforms.
Expedia Group
Expedia Group, also known as Expedia, Inc, is an American online travel company headquartered in Seattle. Founded as a Microsoft division in 1996, it operates Expedia, Hotels.com, and Vrbo.
Expedition 1
Expedition 1, also known as Expedition One, was the first crew to live aboard the International Space Station, arriving November 2, 2000, and starting 25 years of continuous human presence.
Expedition 74
Expedition 74 was the 74th long-duration expedition to the International Space Station, from December 2025 to July 2026, commanded by Michael Fincke and then Sergey Kud-Sverchkov.
Expedition 75
Expedition 75 is the 75th long-duration crew mission to the International Space Station, a roughly eight-month increment commanded by cosmonaut Pyotr Dubrov that began on July 26, 2026.
Expeditionary Fighting Vehicle
The Expeditionary Fighting Vehicle (EFV), begun in 1988 as the Advanced Amphibious Assault Vehicle, was a Marine Corps amphibious vehicle program canceled by Robert Gates in 2011.
Expeditionary Leader-Follower program
The Expeditionary Leader-Follower program, known as ExLF and Leader-Follower Tactical Wheeled Vehicle, is a United States Army program begun in fiscal 2016 in which one manned truck leads unmanned supply convoys.
Expel (company)
Expel is an American managed detection and response provider founded in 2016 and headquartered in Herndon, Virginia, monitoring customers' existing security tools and remediating threats on their behalf.
Expensify
Expensify is a cloud-based expense management platform that helps businesses collect, audit, and reimburse employee expenses. Founded in 2008 and based in Portland, Oregon, it trades on Nasdaq as EXFY.
Experience replay
Experience replay is a reinforcement learning technique in which an agent stores past transitions in a buffer and trains on random samples, proposed by Lin in 1992.
Experimental Advanced Superconducting Tokamak
EAST is a fully superconducting research tokamak at the Institute of Plasma Physics in Hefei, China, the first tokamak with fully superconducting coils, achieving first plasma in 2006.
Experimental Aircraft Association
The Experimental Aircraft Association (EAA) is an international aviation membership association, founded in 1953 by Paul H. Poberezny and headquartered in Oshkosh, Wisconsin, with roots in amateur-built aircraft.
Experimental and research aviation
Experimental and research aviation is the branch of aeronautics that builds and flies aircraft to gather flight data on new designs and technologies rather than carry passengers.
Experimental Boiling Water Reactor
The Experimental Boiling Water Reactor was a prototype direct-cycle reactor at Argonne National Laboratory in Illinois that achieved criticality in 1956, produced 5 MW of electricity, and was shut down in 1967.
Experimental Breeder Reactor II
Experimental Breeder Reactor II was a sodium-cooled pool-type fast breeder reactor in Idaho, built by Argonne National Laboratory and operated from 1964 to 1994 as the test bed for the US breeder program.
Experimental three-phase railcar
The experimental three-phase railcars were two electric test vehicles by AEG and Siemens & Halske that set a 210.2 km/h rail speed record near Berlin in 1903.
Experimental Tokamak (Brazil)
The Experimental Tokamak (Brazil) covers Brazil's experimental tokamaks for fusion research: the spherical ETE at INPE, first plasma in 2000, TCABR at São Paulo, and NOVA-FURG.
Expert choice routing
Expert choice routing is a routing strategy for sparsely activated Mixture-of-Experts models, proposed by Yanqi Zhou and colleagues at Google in 2022, where experts select their top-k tokens.