1. n. Abbreviation for ‘semicolon’, when speaking. “Commands to grind are prefixed by semi-semi-star” means that the prefix is ;;*, not 1/4 of a star.
2. A prefix used with words such as ‘immediately’ as a qualifier. “When is the system coming up?” “Semi-immediately.” (That is, maybe not for an hour.) “We did consider that possibility semi-seriously.” See also infinite.