a long hand that registers seconds or fractions of seconds on the perimeter of the dial
sweep hand in American English
second hand (sense 1)
: also sweep second hand
sweep hand in American English
noun
Horology
a hand, usually a second hand, centrally mounted with the minute and hour hands of a timepiece and reaching to the edge of the dial
Word origin
[1940–45]This word is first recorded in the period 1940–45. Other words that entered Englishat around the same time include: Rh factor, airlift, black box, debrief, sealant