An accomplice is a cooperator or participator, commonly in criminal acts. So you’re an accomplice to the gas station robbery if you distracted the store manager while your partner in crime raided the registers for cash.
Coming from the Old French word complice, which means “a confederate,” an accomplice is an ally or partaker, sometimes in wrongdoing. Novelist Saul Bellow famously said that "when we ask for advice, we are usually looking for an accomplice.” What he means, in more direct terms, is that we run potential plans by others because we're looking for approval or someone to go along with us, not because we truly want their opinion.
n a person who joins with another in carrying out some plan (especially an unethical or illegal plan)
a beguiler who leads someone into danger (usually as part of a plot)
a decoy who lures customers into a gambling establishment (especially one with a fixed game)
a decoy who acts as an enthusiastic customer in order to stimulate the participation of others