say it: SLEE-pee
sleepy is an adjective meaning "ready to fall asleep". It carries one recorded sense.
ready to fall asleep
“beginning to feel sleepy”
“a sleepy-eyed child with drooping eyelids”
“sleepyheaded students”
Forms marked are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for sleepy come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.