Green’s Dictionary of Slang

1. (also bowse) a generic term for any species of dog; thus bowser bag

1851		Manchester Spy (NH) 24 May n.p.: [He] took the liberty of patting old ‘bowse’ on the head to which the animal made no resistance.
1940s		in Campbell & Campbell War Paint 117: [aircraft nose art] Aunt Minnie’s Bowser.
2003		McGill Reed Dict. of N.Z. Sl.

2. (N.Z.) a cheerful fellow.

1972

A. Mitchell Half-gallon Quarter-acre Pavlova Paradise 184: Bowser, a man of spirit.

3. (US campus, also bouser) an ugly woman.

1909		F.H. Tillotson How I Became a Detective 88: A ‘guinea’ or ‘Bowser’ is a woman.
1910		Spokane Press (WA) 22 Sept. 7/3: One old bowser [...] swung on my roof with her mush and put my thatch to the cleaners.
1925		E. Field ‘A French Crisis’ in Facetiae Americana 21: The jibby, bouser, beagle, bawd of every nation.
1980		Eble Campus Sl. Fall 2: bowser – physically unattractive female.
1994		J. Wambaugh Finnegan’s Week 275: These babes are thrashed. I’d rather get cranked and jack off. That way I can have anyone I want instead a these bowsers.

4. (Irish) a troublesome character.

2002

O’Byrne Files: Dublin Sl. Dict. 🌐 Bowser n. Troublesome character.