Feminine rhyme refers to a rhyme of words containing two or more syllables, where the last syllable or syllables is/are unstressed.
An example could be notion and motion or fortunate and importunate. The second syllables of motion and notion remain unstressed, while the second and the third syllables of fortunate and importunate are similarly unstressed.
Feminine rhyme is common throughout poetry. Poe uses it greatly in The Raven, as well as Shakespeare in his sonnets. The rhyme pattern has also become popular in American hip hop music, as a mark of technical skill and complexity.