Which word supports the meaning of decay? round colossal wreck bare

The answer is WRECK.

As a noun, 'decay' is the state of gradual damage or decline in strength, soundness, or prosperity, that is to say, of becoming worse. Similar to the noun 'wreck' that is the state of being damaged, disabled, in ruin or dilapidation.

The other words do not support the meaning of 'decay', because 'colossal' refers to something extremely big, 'bare' is something/someone without any clothes or not covered by anything, and 'round' is something shaped like a ball or circle, or curved.

we need more information in order to answer.

(you didn't attach a copy of the poem, but i'm answering as best as i can)

since a simile compares two unlike things using like or as, it kind of gives an item the ability to do something it can't.

example: "the player was like a tiger on the field"

in this sentence, the simile conveys the idea that the player was fast and strong, like a tiger.