definition of
heartbeat

[1] #1 heartbeat n. [pulse, pulsation, beat] the rhythmic contraction and expansion of the arteries with each beat of the heart; "he could feel the beat of her heart". wn

[2] #2 heartbeat n. [blink of an eye, flash, instant, jiffy, split second, trice, twinkling, wink, New York minute] a very short time (as the time it takes the eye to blink or the heart to beat); "if I had the chance I'd do it in a flash". wn

[3] #3 heartbeat n. an animating or vital unifying force; "New York is the commercial heartbeat of America". wn