The term 'learn by heart' is a phrase that means to commit something to memory. It can be used in reference to a variety of tasks, such as memorizing a poem or studying for an exam. The crossword solutions for this term are MEMORISE (8 letters), NAIL (4 letters), MASTER (6 letters), and MEMORIZE (8 letters). All of these words refer to the act of committing something to memory, either through repetition or intense study.