At first glance, it would seem that the only difference between "blowup" and "blow up" is just a thin space.
Not so, according to the "Thesaurus of American Slang" (Harper & Row), edited by Robert L. Chapman, which lists "America's most important contemporary and historic slang words and phrases" along with their synonyms.The entry for "blowup" - defined as "a fit of anger" - shows 13 different ways of saying it, including "lather," "stew" and "tantrum." Blow up - "to exaggerate the importance of" - gets only seven entries, among them "make a big deal" and "pump up."
If you want to call someone "dumb" - "stupid; mentally sluggish" - but don't want to use that word, the thesaurus offers a selection of 129 other ways to say it, including "dizzy," "dopey" and "three bricks shy of a load."
But if you want to compliment someone by attributing "smarts" - "intelligence, competence" - to him, only nine alternates are listed, among them "brains," "savvy" and "something on the ball."
And, now it's time to shut up - "to be quiet; stop talking" - or "bottle it," "dry up," "zip one's lip."