When you are jerking off in a steam room in anticipation of someone walking in. As they walk in you blow your impeccably timed load all over their face/torso. Requires great self control to give someone a proper steamy hello. Nobody will appreciate a premature steamy hello (PSH).
None of my friends will come to the gym with me after Steve told everyone about the steamy hello I gave him.
It took a couple gym trial memberships to get down the steamy hello, the first couple were PSH.