From SmashWiki, the Super Smash Bros. wiki
A combo is a sequence of attacks that is guaranteed (or very likely) to occur if the first attack hits the enemy. The exact definition of a combo may change from player to player. Some definitions may include:
- Any sequence of attacks that keeps the opponent in hitstun.
- Any sequence of attacks that counts as a combo according to the combo counter (which allows for one consecutive frame of non-hitstun).
- Any sequence of attacks that is very hard to DI (or in certain cases, tech) out of.
- Any sequence of attacks that cannot be DI'd out of if performed perfectly.
- Any sequence of attacks.
- A single attack that consists of multiple hits (see natural combo).
- Any sequence of attacks that prevent the opponent from landing (possibly by tech) or ledge-grabbing.
- Any attack that sends an opponent into a hazard and then leaves them vunerable to other attacks.