Hands In The Sexy Pants, pronounced hitspuhh
i.e. your or your lover's (or both's) hand(s) in one another's "sexy pants", meaning here underwear, or pants, if the person(s) in question are going commando.
To perform h.i.t.s.p., skin must be touched.
we h.i.t.s.p.ed (hitspuhhd) into the early hours of the morning.