ˈglüp noun
( -s )
Etymology: probably of Scandinavian origin; akin to Norwegian dialect glūp hole, gorge, abyss; akin to Swedish dialect glūpa to gape, swallow, Old Frisian glūpa to look, Middle Low German glūpen to look with half-closed eyes, and perhaps to Old English geolu yellow — more at yellow
: an opening in the roof of a sea cave through which incoming waves may force air to rush upward or water to spout intermittently : blowhole 3