What does "regretfully" mean?

In a regretful manner, with regret.

Regretfully

Common synonyms include: apologetically, remorsefully, ruefully, sadly, sorrowfully, unfortunately.

adv

adv ·4 syllables ·Rare ·Advanced level

Adverb

1
In a regretful manner, with regret.
"So after learning a great deal about iron founding and much more about pike fishing, one regretfully took leave of a shop full of kindly characters and proceeded to a worse lot of odours in the brass foundry."
2
Unfortunately, in a manner inspiring or deserving regret; used only as a sentence adverb (to introduce and modify an entire sentence). proscribed

Adverb

"We regretfully reject your offer."

From regretful + -ly.