From Longman Dictionary of Contemporary Englishruefulrue‧ful /ˈruːfəl/ adjective REGRET/FEEL SORRYfeeling or showing that you wish you had not done something a rueful smile —ruefully adverb He smiled ruefully.
Examples from the Corpus
rueful• Then she pulled a rueful face.• Celia and Brassard, who had overheard everything from the outer office, exchanged rueful glances.• Jane looked at her with a rueful smile. 