Answer:
The answer is villanelle.
Explanation:
A villanelle is a nineteen-line poem, constituted of five tercets and a quatrain. The rhyming scheme for those lines is: aba, aba, aba, aba, aba, abaa. Some lines are repeated throughout the poem. The repeated lines are called refrains. Thus, the description given in the question is that of a villanelle. Let's check those characteristics in Dylan Thomas's poem "Do Not Go Gentle Into That Good Night":
(First tercet)
Do not go gentle into that good night, A
Old age should burn and rave at close of day; B
Rage, rage against the dying of the light. A
(Second tercet)
Though wise men at their end know dark is right, A
Because their words had forked no lightning they B
Do not go gentle into that good night. A
(Third tercet)
Good men, the last wave by, crying how bright A
Their frail deeds might have danced in a green bay, A
Rage, rage against the dying of the light. A
(Fourth tercet)
Wild men who caught and sang the sun in flight, A
And learn, too late, they grieved it on its way, B
Do not go gentle into that good night. A
(Fifth tercet)
Grave men, near death, who see with blinding sight A
Blind eyes could blaze like meteors and be gay, B
Rage, rage against the dying of the light. A
(Quatrain)
And you, my father, there on the sad height, A
Curse, bless, me now with your fierce tears, I pray. B
Do not go gentle into that good night. A
Rage, rage against the dying of the light. A
Rhyming scheme: night and the words that rhyme with it - A; day and the words that rhyme with it - B.
Refrains: "Do not go gentle into that good night" and "Rage, rage against the dying of the light".
