A secret synonym could be described as a word you and a friend share as an inside joke, a word that relates a random event known only to a select few, or your mental descriptor for a certain something.
So with that in mind, what would you/do you have as a secret synonym for 'gay' (or any other part of LBT)? Do you glance at yourself in the mirror and think to yourself "I'm especially *fab* today", or point out how 'groovy' that guy/girl is that keeps staring at you?
I'd probably go with the word 'snazzy'. Sometimes when I'm in the city and walking and highly likely stylish gay people walk by me, I'm mentally screaming 'snazzy, snazzy, snazzy!'. Either that or 'sexually charged'. What terms have you got for gay in the verbatim way?