adjective

1. having the same direction throughout its length; having no curvature or angularity a straight line
2. not crooked, bent, bowed, wavy, curly, etc. straight hair
3. upright; erect straight posture
4. level; even a straight hemline
5. with all cylinders in a direct line; in-line: said of some internal-combustion engines
6. direct; undeviating, uninterrupted, etc. to hold a straight course
7. ☆ following strictly the principles, slate of candidates, etc. of a political party
8. following a direct or systematic course of reasoning, etc.; methodical; accurate
9. in order; properly arranged, etc. to put a room straight
10. 1. honest; sincere; upright
    2. reliable; factual straight information
11. outspoken; frank
12. ☆
    1. without anything added or mixed in; undiluted a straight shot of whiskey
    2. not blended with neutral grain spirits
13. not qualified, modified, slanted, etc. a straight denial
14. ☆ at a fixed price per unit regardless of the quantity bought or sold apples at ten cents straight
15. ☆ Slang
    1. normal or conventional, as in one's lifestyle; also, square ()
    2. heterosexual
    3. not using drugs, alcohol, etc.

Etymology: ME streght, pp. of strecchen, to stretch

adverb

1. in a straight line or direction; unswervingly
2. upright; erectly
3. 1. without detour, delay, etc. go straight to bed
   2. without equivocation, circumlocution, etc.; directly tell it straight
   3. without alteration, addition, etc. play the role straight
4. in an honest, law-abiding manner go straight

noun

1. the quality or condition of being straight
2. something straight; specif.,
   1. the straight part of a racetrack between the last turn and the winning post
   2. ☆ Poker a hand consisting of any five cards in sequence: it ranks just above three of a kind and below a flush
3. Slang
   1. a straight, or conventional, person
   2. a heterosexual