A quatrain rhyme scheme is a type of poem that consists of four lines, or quatrains, with a specific rhyme pattern. The most common quatrain rhyme scheme is ABBA, which means the first and third lines rhyme, as do the second and fourth lines. Another popular quatrain rhyme scheme is ABAA, where the first and third lines rhyme, and the second and fourth lines rhyme with each other. ABAB is another quatrain rhyme scheme, where the first and second lines rhyme, and the third and fourth lines rhyme with each other.