The term 'sonnet ending' refers to the last two lines of a sonnet, which are known as the couplet. The couplet is usually used to provide a resolution to the poem's argument or theme. The crossword solutions for this term are EER (3 letters) and SESTET (6 letters). EER stands for 'envoi, ' which is a short concluding stanza that follows the couplet in some sonnets. SESTET is a six-line stanza, which is often used as the final stanza in a sonnet.