Yes, we all know "jizz" is slang for the noun form of ejaculate (likely derived from jism). But there is a way to use the word in polite company...
The characteristic impression given by an animal or plant.
Oxford English Dictionary, Second Edition, 1989.
<http://dictionary.oed.com/cgi/entry/00123865> (26 February 2002)
The OED cites usage in the UK, mainly in bird and plant identification, going back to 1922. Some American usage is usually associated with birding as well:
All of these factors combined; the shape, posture and flight are lumped together to form a general impression of the bird. Birders call this the Jizz. It takes practice and time to get to know birds this well. Jizz should be combined with field marks to come up with an accurate identification of a bird. "Become a Better Birder," Fieldfare Web Site, <http://www.fieldfare.com/birding.html> (26 February 2002)
The etymology is uncertain. Some people suggest a corruption of "gestalt," others of "guise" (19th century Scottish gizz). Birding lore credits a World War 2 military term, GISS, for "General Impression, Shape, and Size," used to describe the perceptual framework pilots needed to shoot enemy aircraft quickly, but this may be an urban legend (no documented usage in the Australian or UK RAF), and the OED shows earlier usage.
David McDonald, "Re: The Etymology of Jizz," 23 August 1995, Birding-Aus Mail Archive, <http://menura.cse.unsw.edu.au:1080/1995/08/msg00056.html> (26 February 2002)