Noun. An uncircumcised penis. The "G" is indeed silent when pronouncing this ugly word. Not to be confused with a "nard" which is some kind of weird cracker slang for testicle.
A Gnard is most likely the kind of uncircumcised penis that takes you by surprise, either on a nice American boy whom you would never suspect, or a man you've been with 6 months to a year and never realized he had a little extra downstairs.
"I fear the penis of a French man--they are likely to have a gnard."