Meaning of MONOTONE in English

MONOTONE

mon ‧ o ‧ tone /ˈmɒnətəʊn $ ˈmɑːnətoʊn/ BrE AmE noun [singular]

a sound or way of speaking or singing that continues on the same note without getting any louder or softer, and therefore sounds very boring:

He answered all the lawyer’s questions in a dull monotone.

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.