Pulse, water hammer
A jerky pulse that is full and then collapses because of aortic insufficiency (when blood ejected into the aorta regurgitates back through the aortic valve into the left ventricle).
This type of pulse was likened to a water hammer, a Victorian toy consisting of a glass tube filled partly with water or mercury in a vacuum.
The water or mercury produced a slapping impact when the glass tube was turned over.
Also called a Corrigan pulse or a cannonball, collapsing, pistol-shot, or trip-hammer pulse