"monotonous" in the adjective sense
1. humdrum, monotonous
tediously repetitious or lacking in variety all work and no play"
"a humdrum existence
"nothing is so monotonous as the sea"
2. flat, monotone, monotonic, monotonous
sounded or spoken in a tone unvarying in pitch
"the owl's faint monotonous hooting"
Source: WordNet® (An amazing lexical database of English)
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