A Mono-rhyme is a poem with just one rhyme at the end. Very simple. A. That means that every line ends with the same rhyme.
Rhyme, time, dime, lime, to name just a few words.
A master in mono rhyme was Shell Silverstein. He wrote for Bobby Bare the album Lullaby's, Legends and Lies, a work filled with alliterations, and poetic masterpieces.