present participle of stand fast

(video games) The ability to travel instantaneously between previously discovered locations in an open world. / Used other than figuratively or idiomatically: see fast, travel.

Occurring in large numbers and rapidly.

(nuclear physics, engineering) A nuclear reactor with no moderator, using fast neutrons directly in a controlled fission chain reaction without slowing them down; this allows for a much more compact reactor, and causes the reactor to use fissile material much more efficiently, and to generate larger quantities of high-energy neutrons which can be used for breeding more fissile material or producing other useful radioactive nuclides, but requires the use of highly-enriched uranium (at least 20% uranium-235) or other fuel containing a similarly high concentration of fissile material.

plural of fast reactor

simple past tense and past participle of fast-track

(e.g. of a river) Flowing at a swift, rapid rate.

(programming) To report immediately any condition likely to cause a failure, rather than attempting to continue.

simple past tense and past participle of fail fast

Third-person singular simple present indicative form of fail fast