1.  blowhole(n = noun.body) - the spiracle of a cetacean located far back on the skull;
is a kind of spiracle
is a part of blower, cetacean, cetacean mammal

2.  blowhole(n = noun.artifact) vent, vent-hole, venthole - a hole for the escape of gas or air;
is a kind of hole
is a part of air duct, air passage, airway
has particulars: smoke hole

1.  A cavern in a cliff, at the water level, opening to the air at its farther extremity, so that the waters rush in with each surge and rise in a lofty jet from the extremity. [1913 Webster]

2.  A nostril or spiracle in the top of the head of a whale or other cetacean. [1913 Webster]
" There are two spiracles or blowholes in the common whales, but only one in sperm whales, porpoises, etc." [1913 Webster]

3.  A hole in the ice to which whales, seals, etc., come to breathe. [1913 Webster]

4.  An air hole in a casting. [1913 Webster]

N  airpipe, air pipe, air tube, airhole, blowhole, breathinghole, venthole, shaft, flue, chimney, funnel, vent, nostril, nozzle, throat, weasand, trachea, bronchus, bronchia, larynx, tonsils, windpipe, spiracle, ventiduct, ventilator, louvre, jalousie, Venetian blinds, blowpipe, pipe, jhilmil, smokestack, screen, window screen, ' artificial lung, iron lung, heart and lung machine.