A trope is a figure of speech that uses language in a nonliteral way to create meaning, often through metaphor, simile, metonymy, or irony. Poets use tropes to make an idea feel fresh, surprising, or more exact than plain description.
Because the word can also mean a repeated image or familiar pattern in literature, context matters, but in poetry it usually points to figurative language.
Example
Dawn laid a gold coin on the sill,
then took the night by the sleeve and ran.
The moon, a patient candle, watched
as silence opened like a fan.