in love is an adjective meaning "marked by foolish or unreasoning fondness". It carries one recorded sense.
marked by foolish or unreasoning fondness
“he was infatuated with her”
“Narcissus was a beautiful Greek youth who became enamored of his own reflection”
Definitions, synonyms and semantic relations for in love come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.