What is the dictionary definition and the part of speech of the word “rival” used in “rival T-shirts”?

Question

I came across the phrase like "wear rival T-shirts". I'm not sure which is the matching definition of the word "rival" in dictionaries and what is its part of speech —— a noun?

The phrase is in this sentence:

the Rubios wore rival T-shirts. “Mr. Right,” read his. “Mrs. Always Right,” declared hers.

Answer 1

RIVAL

noun

1.a person or thing competing with another for the same objective or for superiority in the same field of activity: I have two favorite teams, Arsenal, and any team playing their rival, Tottenham.

The Rubios is shorthand for a married couple. Mr. Right is the husband and Mrs. Always Right is the wife. They are rivals only in a tongue-in-cheek sense.

I.E. this was a play on the word designed to draw a laugh.