'Regretfully' definitions:
Definition of 'regretfully'
From: WordNet
adverb
With regret (used in polite formulas); "I must regretfully decline your kind invitation"
Definition of 'Regretfully'
From: GCIDE
- Regretful \Re*gret"ful\ (-f?l), a. Full of regret; indulging in regrets; repining. -- {Re*gret"ful*ly}, adv. [1913 Webster] re-group