The three crossword solutions for the term 'Christmas Carol Opener' are 'HARK', 'ADESTE', and 'OCOME'. 'HARK' is an imperative verb meaning to listen or pay attention, and is the opening word of the popular Christmas carol 'HARK! The Herald Angels Sing'. 'Adeste' is a Latin phrase meaning 'O come', and is the opening line of the carol 'Adeste Fideles'. Lastly, 'Ocome' is a shortened version of the Latin phrase 'O come, all ye faithful', which is the opening line of the carol 'O Come, All Ye Faithful'.