​(of the air or climate) warm and slightly wet. These ferns will grow best in a humid atmosphere. The island is hot and humid in the summer.

(of the air or climate) warm and damp. These ferns will grow best in a humid atmosphere. The island is hot and humid in the summer.

There are four meanings listed in OED's entry for the adjective humid. See 'Meaning & use' for definitions, usage, and quotation evidence.

[uncountable] ​the amount of water in the air. Instruments constantly monitor temperature and humidity. high/low humidity. 70% humidity.

conditions in which the air is very warm and damp. These plants need heat and humidity to grow well. The humidity was becoming unbearable.

The quality or condition of being humid; moistness, dampness. relative humidity (of the atmosphere) in Meteorology, the amount of moisture which it contains as ...

noun /hjuːˈmɪdɪfaɪə(r)/ /hjuːˈmɪdɪfaɪər/ a machine used for making the air in a room less dry see also dehumidifier.

(of air and weather conditions) containing extremely small drops of water in the air: New York is very hot and humid in the summer.

noun NAmE//hyuˈmɪdəˌfaɪər// a machine used for making the air in a room less dry see dehumidifier

The Canadian Oxford Dictionary (2 ed.) Edited by: Katherine Barber. Publisher: Oxford University Press. Print Publication Date: 2004.