hum noun
ADJ. faint, soft | low | high-pitched | constant, continuous, steady I could hear the constant hum of distant traffic. | background
VERB + HUM hear
PREP. ~ of the background hum of the air-conditioning
hum verb
ADV. quietly, softly | happily | tunelessly | along humming along with the music
VERB + HUM begin to He began to hum, somewhat tunelessly.
PHRASES hum to yourself She was humming softly to herself.
You can also check other dicts: hum (English, 中文解释 ), wordnet sense, Collins Definition