Green’s Dictionary of Slang

1. (drugs) a drug smuggler who swallows carefully wrapped drugs to take them through customs.

1986

Sun. Times 26 Oct. 3: Customs investigators at Heathrow airport have discovered more than 100 Nigerians on flights from Lagos attempting to smuggle heroin packed inside contraceptive sheaths, which are swallowed or inserted in anal and vaginal passages. They are known to customs officers as ‘stuffers and swallowers’.

2. (Aus.) a derog. term for a woman [she swallows the semen after performing fellatio].

1987		K. Lette Girls’ Night Out (1995) 187: Surfers are an amphibious, beach-dwelling species, who hunt in packs for females with ‘margarine legs’. You know, easily spread. Chicks are nicknamed bush pigs, swamp hogs, maggots, spitters or swallowers.
2001		D. Jenkins Money-Whipped Steer-Job 154: I’m just your average money winner out here who scores his share of pussy [...] and it don’t matter none to me whether they’re spitters or swallowers.