nelly /nɛli/noun 4adjective 1forms 3phrases 1 noun4 •(slang, offensive) An effeminate homosexual man. •(slang) A person's life. •(UK, slang) A silly person. •A giant petrel, Macronectes giganteus and Macronectes halli. adjective1 •(slang) Unmanly; effeminate.Some of the nelliest boys unable to get or keep a job, some of the toughest girls breaking their bodies trying to do men's work. — 2012 formsnellies · nellier · nelliest Phrases with nelly not on your nellyAbsolutely not; under no circumstances.