the sound a man makes when he pics'. when a man does not know what is, he thinks of something to do and it is usually of the pic'ing nature. blah-thup is a term used to say, "hey man! i caught you pic'ing!"
James caught adam in the midst of a pic' and yelled "blah-thup".
by cabby11 November 14, 2010
Can you define these popular missing words?