Green’s Dictionary of Slang

(W.I.) proud, boastful, showy.

1869		H.G. Murray ‘Tom Kittle’s Wake’ in D’Costa & Lalla Voices in Exile (1989) 89: Dat Mass William Hinds [...] him is a regilar bosify Bony.
1966		(con. 1940s) L. Bennett ‘Solja Bwoys’ in Jamaica Labrish 97: Go train up strong an fit, / Nice up yuh self, look boasify, / Galang go do yuh bit.
1980		(con. 1950s) M. Thelwell Harder They Come 122: Coo ’pon the nyaman dem! What a way dem boasie, eh?
1983		V. Bloom ‘Easta Bun’ in Touch Mi, Tell Mi 34: Miss Cassy get up one mawnin’ / Boasify cyan done.
1990		L. Goodison Baby Mother and King of Swords 70: The girl was very stuck-up-looking, boasy and conceited.