A palinode or palinody is an ode in which the writer retracts a view or sentiment expressed in an earlier poem. The first recorded use of a palinode is in a poem by Stesichorus in the 7th century BC, in which he retracts his earlier statement that the Trojan War was all the fault of Helen. 
An important example of a palinode is that of Socrates in the Phaedrus in which his first major speech disparages the "mania" of Eros and its part in human affairs, while his second one (commonly known as the palinode of Socrates) praises Eros. As he says, "love was not sent from the Gods for the utility of the lover and his beloved. But, on the contrary, it must now be shown by us that a mania of this kind was sent by the Gods, for the purpose of producing the greatest felicity."
The word comes from the Greek παλινῳδία from πάλιν (palin, meaning 'back') and ᾠδή ("song"); the Latin-derived equivalent "recantation" is an exact calque (re- meaning 'again' and cant- meaning 'sing').
Chaucer's Retraction is one example of a palinode.
In 1895, Gelett Burgess wrote his famous poem, the Purple Cow:
- I never saw a purple cow.
- I never hope to see one.
- But I can tell you anyhow
- I'd rather see than be one.
Later in his life, he followed it with this palinode:
- Ah yes, I wrote the purple cow!
- I’m sorry now I wrote it!
- But I can tell you anyhow,
- I’ll kill you if you quote it!
- Nothing makes me sicker
- than liquor
- and candy
- is too expandy