The term 'BUG TO NO END' can be broken down into three crossword solutions: PESTER (6 letters), ANNOY (5 letters), and IRK (3 letters). PESTER is defined as to harass or torment persistently, ANNOY is defined as to cause trouble, irritation, or vexation, and IRK is defined as to cause weariness, vexation, or irritation. All three words are synonyms for the phrase 'bug to no end, ' which means to bother or irritate someone continuously.