Doggerel is verse that sounds clumsy, flat, or awkward, usually because of forced rhyme, uneven meter, or simplistic word choice. It is often humorous or intentionally light, but the word usually suggests poetry that falls short of serious craft and feels more crude than musical.
The Scottish poet William McGonagall is famous for his doggerel and enjoys the dubious distinction of being regarded as the world's worst poet.
Example
The moon is green, the chairs all sing,
I lost my hat last Tuesday spring;
My boots ate jam, the clock went haywire,
And every fence was built of wire.
[n] a comic verse of irregular measure; "he had heard some silly doggerel that kept running through his mind"