Abbr. h., H.
3. a. Requiring great effort or endurance: a hard assignment. b. Performed with or marked by great diligence or energy: a project that required years of hard work. c. Difficult to resolve, accomplish, or finish: That was a hard question. d. Difficult to understand or impart: Physics was the hardest of my courses. Thermodynamics is a hard course to teach.
4. a. Intense in force or degree: a hard blow. b. Inclement: a long, hard winter.
5. a. Stern or strict in nature or comportment: a hard taskmaster. b. Resistant to persuasion or appeal; obdurate. c. Making few concessions: drives a hard bargain.
6. a. Difficult to endure: a hard life. b. Oppressive or unjust in nature or effect: restrictions that were hard on welfare applicants. c. Lacking compassion or sympathy; callous.
7. a. Harsh or severe in effect or intention: said some hard things that I won't forget. b. Bitter; resentful: No hard feelings, I hope.
8. a. Causing damage or premature wear: Snow and ice are hard on a car's finish. b. Bad; adverse: hard luck.
9. Proceeding or performing with force, vigor, or persistence; assiduous: a hard worker.
10. a. Real and unassailable: hard evidence. b. Definite; firm: a hard commitment. c. Close; penetrating: We need to take a hard look at the situation. d. Free from illusion or bias; practical: brought some hard common sense to the discussion. e. Using or based on data that are readily quantified or verified: the hard sciences.
11. a. Marked by sharp outline or definition; stark. b. Lacking in delicacy, shading, or nuance.
12. a. Metallic, as opposed to paper. Used of currency. b. Backed by bullion rather than by credit. Used of currency. c. High and stable. Used of prices.
13. a. Durable; lasting: hard merchandise. b. Written or printed rather than stored in electronic media: sent the information by hard mail.
14. Erect; tumid. Used of a penis.
15. a. Having high alcoholic content; intoxicating: hard liquor. b. Rendered alcoholic by fermentation; fermented: hard cider.
16. Containing dissolved salts that interfere with the lathering action of soap. Used of water.
17. Linguistics. Velar, as in c in cake or g in log, as opposed to palatal or soft.
18. Physics. Of relatively high energy; penetrating: hard x-rays.
19. High in gluten content: hard wheat.
20. Chemistry. Resistant to biodegradation: a hard detergent.
21. Physically addictive. Used of certain illegal drugs, such as heroin.
22. Resistant to blast, heat, or radiation. Used especially of nuclear weapons.
hard and fast
Defined, fixed, and invariable: hard and fast rules.
hard of hearing
Undergoing great difficulty: Under the circumstances, he was hard put to explain himself.
hard up Informal
In need; poor.
[Middle English, from Old English heard.]