Green’s Dictionary of Slang

1. (US short order) of eggs, ‘sunny-side up’.

1899		Atlanta Constitution 17 July 5/4: ‘Ham and — straight up’ gave the patron ham with eggs that were soft on top.
1906		‘O. Henry’ ‘The Brief Debut of Tildy’ in Four Million 253: Any quantity of things on the iron and in the pan and straight up and on the side.
1923		El Paso Herald (TX) 31 Jan. 8/2: For two fried eggs there are various terms [...] ‘bride and groom,’ ‘straight up two’ and ‘two moons looking at you’.

2. (US prison) of a sentence, served without parole; also as adv.

1969

‘Iceberg Slim’ Pimp 32: He had just done a two-year ‘bit’ straight up.

3. simple.

1981

M. Baker Nam (1982) 30: There probably wasn’t going to be as much action as I wanted if I were just a straight-up infantryman.

4. (US) of drinks, served without ice cubes.

1971		L. Sanders Pleasures of Helen 225: She was holding a cigarette and martini (straight up) in one hand.
1985		A. Payne ‘Minder on the Orient Express’ in Minder [TV script] 80: Straight up means no ice, Arthur.
1990		J. Wambaugh Golden Orange (1991) 36: She chose an Alabama slammer [...] Straight up.