Green’s Dictionary of Slang

dash adj.1

[backform. f. have a dash of lavender under lavender adj.]

(US gay) latently homosexual.

[US]B. Rodgers Queens’ Vernacular 60: dash (? fr ‘dashing’ or sl dash = a tiny bit) 1. latent homosexual 2. willing to give homosexuality a try ‘On the exterior he looks happily married, but he’s dash around the edges.’.