black widown.1. Any of several venomous spiders of the genus Latrodectus, the females of which have a black shiny body with red markings, often in the shape of an hourglass on the abdomen, and can inflict a dangerous bite.2. A woman who kills her husband or lover, especially one who kills multiple husbands or lovers.[From the fact that the female sometimes eats its mate.]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.black widow or black widow spidern (Animals) an American spider, Latrodectus mactans, the female of which is black with red markings, highly venomous, and commonly eats its mateCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014black? wid?ow n. 1. a venomous black spider, Latrodectus mactans, of warm regions, including the U.S.: the female has an hourglass-shaped red mark on the underside of the abdomen. 2. any venomous spider of the cosmopolitan genus Lactrodectus. [1910?15] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.black widow A very poisonous spider, the female of which has a black body, typically with a red, hourglass-shaped mark on the underside. The female often eats the male after mating.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.