A feminine ending is a line of verse that finishes with an extra unstressed syllable after the expected metrical pattern. In English poetry, it often gives the line a softer, more fluid ending and can slightly loosen the beat. It is the opposite of a masculine ending, which ends on a stressed syllable.
Example
The candle flickered near the windowpane,
Its pale light trembling over book and chair,
And shadows leaned together in the rain.