Green’s Dictionary of Slang

tang out v.

[tang n.2 ]

(US campus) to abandon, to put an end to.

[US]Eble Campus Sl. Mar. 4: tang out – to desert, to call it quits.
[US]Eble Sl. and Sociability 30: In college slang out is the most productive particle: [...] tang out ‘abandon, put an end to.’.