Emily Dickinson Lexicon

MUSE, n. [s as z; L. musa; Gr. μουσα. See the Verb.]

1. Properly, song; but in usage, the deity or power of poetry. Hence poets in modem times, as in ancient, invoke the aid of the Muse or muses, or in other words, the genius of poetry. Granville commands; your aid, O Muses, bring, / What Muse for Granville can refuse to sing? Pope.
2. Deep thought; close attention or contemplation which abstracts the mind from passing scenes; hence sometimes, absence of mind. As in great muse, no word to creature spake. Spenser. He was fill'd / With admiration and deep muse to hear / Of things so high and strange. Milton.