From Longman Dictionary of Contemporary Englishold troutold troutBritish English spokenUNPLEASANT an unpleasant or annoying old person, especially a woman → trout
Examples from the Corpus
old trout• Consequently, as older trout die they are not replaced and in time the trout population disappears.• And she hadn't said when the disagreeable old trout was going to walk.• She had insisted on coming with me to refresh, so she said, her memory of that ghastly old trout. 