Definition of bomb
A bomb is a hand that is very strong. Bomb is not an official term, but a common phrase in the vernacular. Generally, we will want to "slowplay" our bombs, that is, play them passively so that your opponent stays hooked. For example, if we have a pair of jacks in our hand and the flop shows 2-2-J, we have a bomb, a hand that is almost unbeatable (except against a four of a kind, of course).
Should you play your bombs fast or slow?
The answer to the question depends on the texture of the flop or the board. If the board is dry, it is best to play passively. If the board is dynamic, offering several draws, it is better to play quickly, even with a bomb! Let's see 2 examples.
You have 99 in hand on 9-J-Q. You certainly have a bomb, but the board is dynamic. And if there's a flush draw, you'll want to play that flop as quickly as possible. Bet big and raise big. Faced with a raise, re-raise!
Another situation, you have 55 in your hand on 2-5-5. You have the best possible hand which obviously qualifies as a bomb! The draws are almost non-existent, the board is rainbow (spades, clubs and hearts) so there are no color draws. On this type of board, play slowly! The check and call are to be preferred.