very sorry; remorseful; apologetic
Archaic expression of deep apology or regret, equivalent to modern 相済まない. Used in historical or formal literary contexts.
See also: 相済む (あいすむ) · 相済まない (あいすまない)
"I am deeply sorry," said the samurai, bowing his head.
Archaic negative form of 相済む (あいすむ), a compound of 相 (mutual) and 済む (to finish, be settled). The exact historical derivation is uncertain, but the expression is conventionally associated with formal apology.