plural of Fast

present participle and gerund of fast

abstinence or mortification for religious reasons, especially abstinence from food / abstinence from food, limiting caloric intake, for medical or health reasons, dieting

The quality or state of being strongly attached; firmness, secureness, tenacity. / The quality or state of moving quickly; quickness, rapidity, swiftness.

plural of fastness

plural of fast

Third-person singular simple present indicative form of fast

simple past tense and past participle of fast

(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