Mūsa refers to the muse, a figure from Greek mythology embodying inspiration in the arts and sciences. In the context of Vergil's Aeneid, particularly in the opening lines of Book 1, Mūsa represents divine inspiration, guiding the poet as he embarks on narrating the epic tale of Aeneas and his quest. This invocation sets the stage for the themes of fate and divine intervention that permeate the poem.