labionasal

from The Century Dictionary.

• Formed or pronounced by the coöperation of the lips and the nose.
• noun An articulate sound produced by the cooperation of the lips and the nose, or the letter or character representing such sound, namely, masculine In pronouncing m, the lips are closed and nasal passages are open.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Phonetics) Formed by the lips and the nose.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective medicine Labial and nasal; pertaining to both the upper lip and the nose, or to both lips and the nose.