Hygroscopic

Part of speech: adjective (a.)

1. Of or pertaining to, or indicated by, the hygroscope; not readily manifest to the senses, but capable of detection by the hygroscope; as, glass is often covered with a film of hygroscopic moisture.

2. Having the property of readily inbibing moisture from the atmosphere, or of the becoming coated with a thin film of moisture, as glass, etc.