hu ‧ mid ‧ i ‧ fy /hjuːˈmɪdəfaɪ, hjuːˈmɪdɪfaɪ/ BrE AmE verb ( past tense and past participle humidified , present participle humidifying , third person singular humidifies ) [transitive]
to add very small drops of water to the air in a room etc because the air is too dry