Definition of bullshit:
blatantly false statements, generally made with intent to deceive; a card game
in which the object is to bluff about cards laid down and to determine when one's opponents are bluffing
"that's bullshit! I called your office and they said you never came in!"
"I think you're bullshitting. Let's just call your office and see if you even came in."
an expression of disbelief at what one has just heard