Cumbust

To have performed sexually at such a profound level that the utilised orifice has caught fire due to friction.

This could be down to a number of factors:
1. Overly fricative appendage surfaces, e.g. a scaley penis
2. Use of a lube with an insufficient smoke point for the activity, e.g. high-velocity anal sex lubricated with Butter (176°C) rather than Ghee (250°C) that meets an emulsifier, e.g. 'Baby Gravy', thus overcoming a natural fire retardant, e.g. 'Fannybatter'

Example 1 is pure friction but usually occurs before Cum enters the picture so is not relevant to this analysis
Example 2 is the true Cumbust in that it is down to the complex chemical interations of these substances when extreme kinetic energy is applied to them

Bob - Jesus, did you see what happened when Bill banged Brenda's Bum hole?

Babs - Nope, wtf?
Bob - She Cumbusted, flew into low earth orbit, left a trail of winnets in the night sky that looked like a meteor shower
Babs - Shit, talk about blasted into maternity by a guided muscle....

Campuflage

The disguise adopted by straights to blend into non-straight environments

Barry - "What do you think of this flowery shirt and feather boa combination for the Blue Oyster Bar?"

Karl - "Absolutely, fantasic Campuflage, no-one will look twice at you with clothes that uglyI"