Definition of fast :
1. A time of fasting, whether a day, week, or longer time; a period of abstinence from food or certain kinds of food; as, an annual fast.
2. Abstinence from food; omission to take nourishment.
3. Firm against attack; fortified by nature or art; impregnable; strong.
4. Firm in adherence; steadfast; not easily separated or alienated; faithful; as, a fast friend.
5. Firmly fixed; closely adhering; made firm; not loose, unstable, or easily moved; immovable; as, to make fast the door.
6. Given to pleasure seeking; disregardful of restraint; reckless; wild; dissipated; dissolute; as, a fast man; a fast liver.
7. In a fast or rapid manner; quickly; swiftly; extravagantly; wildly; as, to run fast; to live fast.
8. In a fast, fixed, or firmly established manner; fixedly; firmly; immovably.
9. In such a condition, as to resilience, etc., as to make possible unusual rapidity of play or action; as, a fast racket, or tennis court; a fast track; a fast billiard table, etc.
10. Moving rapidly; quick in mition; rapid; swift; as, a fast horse.
11. Not easily disturbed or broken; deep; sound.
12. Permanent; not liable to fade by exposure to air or by washing; durable; lasting; as, fast colors.
13. Tenacious; retentive.
14. That which fastens or holds; especially, ( Naut.) a mooring rope, hawser, or chain; - called, according to its position, a bow, head, quarter, breast, or stern fast; also, a post on a pier around which hawsers are passed in mooring.
15. The shaft of a column, or trunk of pilaster.
16. To abstain from food; to omit to take nourishment in whole or in part; to go hungry.
17. To practice abstinence as a religious exercise or duty; to abstain from food voluntarily for a time, for the mortification of the body or appetites, or as a token of grief, or humiliation and penitence.
18. Voluntary abstinence from food, for a space of time, as a spiritual discipline, or as a token of religious humiliation.
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fast (part of speech: adjective)
hasty (part of speech: adjective)