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Webster 1828 Edition

adv.

In an unwelcome or unpleasing manner.

unacceptably ‎(comparative more unacceptably, superlative most unacceptably)

Not within the limits of what is generally considered to be acceptable.

The levels of lead in marine hull paints are still unacceptably high.

Your comments are unacceptably provocative.

in an unacceptable way