cheap (inexpensive) prostitute.(obs.) word from Victorian England. threepenny (thrup'ny) was the price, upright was the position (to facilitate speed, therefore rapid turnover of customers), "the deed" was frequently done in alleyways. Known use found in Bertolt Brecht's "The Beggar's Opera".
" 'es got the pox from seeing too many thrup'ny uprights" "A Lady?, Hell, she's naught but a threepenny upright."
term arising from the military use of a 24 hour clock (0800 for 8 AM and 2000 for 8 PM- for those people who can't tell if its day or night) e.g. zero three hundred is 3 AM. zero dark hundred is usually inferred to as being sometime after last call and before reville...anytime between 2 and 5 AM. In other words, Waaay to fucking early to get up and go on watch, or on a 20 mile hike.
Whaddaya mean 'patrol'? it's still zero dark hundred!