sweep-second hand
sweep-sec·ond hand
(swēp′sĕk′ənd)n.
A long hand on a clock or watch that measures seconds by moving the space of a minute for each second. Also called sweep hand.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.