metaphor [Gr.,=transfer], in rhetoric, a figure of speech in which one class of things is referred to as if it belonged to another class. Whereas a simile states that A is like B, a metaphor states that A is B or substitutes B for A. Some metaphors are explicit, like Shakespeare's line from As You Like It: "All the world's a stage." A metaphor can also be implicit, as in Shakespeare's Sonnet LXXIII, where old age is indicated by a description of autumn:
That time of year thou mayst in me beholdA dead metaphor, such as "the arm" of a chair, is one that has become so common that it is no longer considered a metaphor.
Where yellow leaves, or none, or few, do hang
Upon those boughs which shake against the cold,
Bare ruined choirs, where once the sweet birds sang.