Finger bum flank

The act of kissing ones partner standing face on and flanking a sneaky finger into the anus to cause surprise

Michael was under the impression dale just wanted a kiss. Little did he know Reza was setting him up, face on for a finger bum flank

finger flank

when you slip your finger in your girls butt hole at the movies.

"I finger flanked my girls at the movies my dude"