Final answer:
The participle 'competing' in the sentence acts as a participial adjective, providing additional description to the noun 'teams'.
Step-by-step explanation:
The participle in the sentence “The competing teams shook hands after the game was over” is “competing”. It functions as a participial adjective describing the noun “teams”.
This participle provides more information about the teams, indicating that they were in the process of competing when the action of the sentence took place.