- Central European Initiative (see Wikipedia article on topic)
- Cycle Engineers' Institute, one of three screw thread standards contributing to the Whitworth threads standards set (see "British Standard Whitworth" Wikipedia article for more information)
- (BDSM) Initialism of cum-eating instructions: written or recorded instructions directing a submissive to consume semen.
- 2014, "Erotic Girl 4 ALL Your Pleasures", Are You SERIOUS About EDGING? JOI ? CEI ? Let's See How Much Will Power You Have (on newsgroup alt.penthouse.sex.femdom)
- 2015, "Humiliate You", Are You A Little Dick Man?? WANT Little Dick Humiliation - JOI with A Side of CEI (on newsgroup alt.sex.femdom)