nidan verb (upper class) with 'bu' ending (archaic), intransitive verb
Archaic intransitive verb. In modern Japanese, 詫びる (わびる) is used instead. This form appears only in classical texts.
See also: 詫びる
古語では「わぶ」と読み、謝る意味で使われた。
In classical Japanese, it was read as 'wabu' and used to mean 'to apologize'.