Wiktionary
adv. 1 Through the collaborative efforts of multiple contributors, as a team or committee assigned to accomplish a goal; especially as known for protracted proceedings, a lack of responsiveness, or undesired results. 2 (context figuratively sometimes humorous English) With any of the results cynically attributed to committee projects, e.g. unnecessary complexity, inconsistency, logical flaws, lack of a unifying vision, banality, lack of style or character, etc.
Usage examples of "by committee".
As the old joke goes, 'the definition of a camel is a horse designed by committee'.
Remarried by then-rny grandfather had been killed, a typical stupid error, by Committee Police.
It was part of the game to pretend admirals were still fleet commanders, even though everyone knew command was actually exercised by committee these days.