Pronounced "TOOK-us OY-f'n tish." Many variant spellings. Literally "ass on the table," it's a Yiddish phrase meaning a serious atmosphere for talk or negotiation. Closest US-English equivalents are probably "No BS" or "(Let's get down to) brass tacks." Often used in a tone of exasperation. Generally recommended for use within members of the same sex.
"Elliot, come into the dining room. We need to make travel plans NOW or they won't get done."
"But Uncle Bernie, the game starts in half an hour."
"Plenty of time if you stop fooling around. Cmon: tuchus oyfn tish."