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Webster 1828 Edition

adv.

With one uniform tone; without inflection of voice.

monotonously ‎(comparative more monotonously, superlative most monotonously)

In a manner that is tedious, repetitious or lacking in variety.
She worked monotonously at the assembly line.
In a droning manner, that does not change pitch.
The minister spoke monotonously and his congregation began to doze.

in a manner that is tedious

in a droning manner