Definition of combo
The word combo is the diminutive of combination in English. Depending on the discipline in which it is used, combo will have a multitude of meanings. In poker, we will use the word combo to define 2 particular things. Firstly, combo will define possible combinations in our opponent's range. If we take a hand like AK, we will be able to form 1preflop different combos using all Hold’em cards (AK of hearts, AK of spades, A of spades K of clubs, etc). These 1preflop combos represent 1preflop combos out of the 132preflop possible combos. (When you receive 2 random cards at Hold’em, you will receive one of the 132preflop possible combos. At a specific point in a hand, you may ask yourself, "Does Bad Guy have any AK combos in his hand because he doesn't have 3bet preflop"?
The combo draw or combos prints
If you play Omaha, you will often hear the expression "combo draw". The expression is also used in Hold’em, but it is more common in Omaha. If you have a hand like KQ in spades on J-T-2 with two spades, you will be said to have a "combo draw", i.e. a hand that will give you a multitude of outss. By combo, we mean any combination of turn + river that could help you. Here, any 9, A or spades would help you. Perhaps even a K or Q could help you.