Someone who comments on things. This term is usually in reference to sports announcers, such as John Madden, Pat Summerall, Brent Musberger, Bob Costas, Frank Gifford, etc.

Com"men*ta`tor (?), n. [L. commentator: cf. F. commentateur.]

One who writes a commentary or comments; an expositor; an annotator.

The commentator's professed object is to explain, to enforce, to illustrate doctrines claimed as true. Whewell.

© Webster 1913.