I. noun a portable breathing apparatus for divers, consisting of cylinders of compressed air strapped on the diver’s back, feeding air automatically through a mask or mouthpiece. II. verb — [no obj.] 1.
‹dated› swim under water using an aqualung
• you oughtn’t to aqualung by yourself.
– origin 1950s (originally a proprietary name in the US): from Latin aqua ‘water’ + lung.