What is the name of this tabletop multiplayer card game
I always called it B.S. growing up, but it is also knows as Cheat, as well as a couple other names.
From Wikipedia:

Cheat (also known as Bullshit, B.S., Bluff, or I Doubt It[3]) is a card game where the players aim to get rid of all of their cards.[4][5] It is a game of deception, with cards being played face-down and players being permitted to lie about the cards they have played.