caltrop(redirected from Jack rock)
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1. See water chestnut.
2. Any of various plants bearing small spiny fruits, especially of the genera Tribulus and Kallstroemia.
3. A metal device with four projecting spikes so arranged that when three of the spikes are on the ground, the fourth points upward, used as a hazard to pneumatic tires or to the hooves of horses.
[Middle English calketrappe, from Norman French and from Old English calcatrippe, thistle, both from Medieval Latin calcatrippa, thistle : possibly from Latin calcāre, to tread on; see calque + trappa, trap (of Germanic origin).]
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.
1. (Plants) any tropical or subtropical plant of the zygophyllaceous genera Tribulus and Kallstroemia that have spiny burs or bracts
2. (Plants) water caltrop another name for water chestnut1
3. (Plants) another name for the star thistle
4. (Military) military a four-spiked iron ball or four joined spikes laid upon the ground as a device to lame cavalry horses, puncture tyres, etc
[Old English calcatrippe (the plant), from Medieval Latin calcatrippa, probably from Latin calx heel + trippa trap1]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
or cal•trap(ˈkæl trəp)
1. any of several plants having spiny heads or fruit, as those of the genera Tribulus and Kallstroemeria.
2. an iron ball with four projecting spikes, one of which always points upward when the ball is placed on the ground: used to obstruct cavalry, vehicles, etc.
[before 1000; Middle English calketrappe, Old English calcatrippe]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
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|Noun||1.||caltrop - tropical annual procumbent poisonous subshrub having fruit that splits into five spiny nutlets; serious pasture weed|
|2.||caltrop - a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits|
|3.||caltrop - Mediterranean annual or biennial herb having pinkish to purple flowers surrounded by spine-tipped scales; naturalized in America|
centaury - any plant of the genus Centaurea
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