rare - редкий
If you are apologetic, you show or say that you are sorry for
causing trouble for someone, for hurting them, or for disappointing them.
The hospital staff were very apologetic but that couldn't really compensate...
`I don't follow football,' she said with an apologetic smile.
`It's of no great literary merit,' he said, almost apologetically.
un- отрицательная приставка.
это слово происходит от apologize - извиняться, просить прощения.
кстати * способы извиниться на наглийском