1. Verb: It describes an action, like "He rushed to catch the train."
2. Noun: It can refer to a sudden surge or a period of intense activity, like "The holiday season brought a rush of customers."
3. Adjective: It can describe something done quickly or in a hurry, like "He gave a rush job to the repairs."
4. Interjection: It can express urgency or excitement, like "Rush! The fire alarm is going off!"
Without the context of a sentence, it's impossible to know the precise word class of "rush."