monotonous
muh-NOT-uh-nusadjMeaning dull because it never changes; always the same
Memory hook MONO-TONE: one note, again and again. Felix plays the same single piano key for an hour: “Plink… plink… plink…” The sound is monotonous.
The monotonous hum of the fan put the baby to sleep.
In context The speaker read every slide in the same flat, monotonous voice, never pausing or changing pitch, and half the audience was soon nodding off.
Similar repetitive, unvarying, humdrum, dull
Opposite varied, lively, interesting
From Greek monotonos, “of one tone”: monos (single) + tonos (tone).