Is there a word or phrase to depict this?

flagrante delicto?

Hang on - I'll check...

Yes - but adultery is not mentioned - but that is the best I can do for now!

Main Entry: fla·gran·te de·lic·to
Pronunciation: fl&-"grän-tE-di-'lik-(")tO, -"gran-
Function: adverb or adjective
Etymology: Medieval Latin, literally, while the crime is blazing
: in the very act of committing a misdeed : RED-HANDED; also : in the midst of sexual activity

Catch him with his pants down?

"caught in the act" though not specific for sex acts.
Noddy's much more colorful.

捉姦在牀 catch adultery in the act...

I decided to use "catch adultery redhanded" for the time being, obviously having been inspired by you all.

oristarA, where the hell are you putting all the information you're getting from this site?

You must be running out of room.

Gus - some of us have BRAINS - they store information.

And cool the blood - but that isn't important right now...

You hate me, don't you dlowan.

Your words cut like razors.

I am bleeding on the floor.

No Gus - I am secretly, shamefully, in love with you.

But you only ever say mean things to me - so I suffer in sound.

Want a paper towel?

The phrase you are looking for is "walked in on'' as in "She walked in on her husband and the blond." or "Everything seemed normal to Bob till he walked in on his wife and the milkman trying to churn butter on the kitchen table." Those words "walked in on" strike terror in the hearts of men, "I can't go home, Millie walked in on me and that babysitter this afternoon." and divorce lawyers, "You can't claim alienation of affection, didn't you say she walked in on you?" They are automatically understood to mean in the act of sexual congress.
"She walked in on us."
"What were you doing?"
"What do you mean, what were we doing? We were putting postage on envelopes."
"You mean you were getting your stamps cancelled, getting your meter punched, getting your..."
"Would you shut up!"
"Getting your ashes hauled?"
"(slow burn..)"


Joe