DCHP-1 Online
Thursday-night soldier Slang, Derog. 
a member of the militia or reserve army, which usually parades one night a week.
- 1949 "Well, I'll be a son of a whore, what're you s'posed to be, a Thursday night soldier."
- 1949 "Well, I'll be a son of a whore, what're you s'posed to be, a Thursday night soldier."