Green’s Dictionary of Slang

(US black) showing off, bragging, often in the ostentatious display of jewellery, expensive clothes, cars etc.

1967		M. Braly On the Yard (2002) 299: You better knock off the highsiding, you degenerate old cocksucker.
1972		‘Soulful Spider’ ‘Pimp in a Clothing Store’ in Milner & Milner (1972) 286: Yessiree, Jack, he’s coming on down high-sidin’, signifyin’ and talkin’ that jive, come ridin’ on by hollering, ‘Hey, you jive malformies, you better get on your job out there, quit your chippying!’.