What is the meaning of Regret?

To feel sorry about (a thing that has or has not happened), afterthink: to wish that a thing had not happened, that something else had happened instead.

To feel sorry about (any thing).

To miss; to feel the loss or absence of; to mourn.

Emotional pain on account of something done or experienced in the past, with a wish that it had been different; a looking back with dissatisfaction or with longing.

Dislike; aversion.

The amount of avoidable loss that results from choosing the wrong action.

regret

nostalgia

regret, repentance

regret

Source: wiktionary.org