(idiomatic) Extremely fast, fast as lightning.

(idiomatic) Extremely quickly.

(Islam) Eid al-Fitr

(informal) Alternative form of quick buck

(chiefly US, set phrase) A period of time characterized by quickly-paced activity, especially involving extravagant or risky conduct, sexual behavior, or other exciting events.

With hands that move very quickly. / Highly efficient at improvisation. / Sexually aggressive. / (obsolete) Greedy, miserly.

(marketing) One who is not an early adopter but begins using a product or service shortly after its introduction.

plural of fast follower

Moving rapidly / Of or relating to a situation in which events follow each other in quick succession / (of a product) That is sold quickly

(nonstandard) Alternative form of breakfast (“meal eaten after fasting”)