fluoxetinePronunciation: /fluːˈɒksətiːn/Definition of fluoxetine noun [mass noun] Medicine a synthetic compound which inhibits the uptake of serotonin in the brain and is taken to treat depression. Also called Prozac ( trademark).Origin: 1970s: from fluo(rine) + ox(y) + -etine (perhaps from e + a blend of toluene and amine)fluoxetine in other Oxford dictionaries Definition of fluoxetine in the US English dictionary