An acronym for "suck my dick". Widely used across the intergalactic web, and in general conversation.
guy: my mom made me pancakes
dude: ur mom can smd
in real life:
guy: omg you're well ugly man
dude: how about smd?
A more effective and stronger way of saying "penis". May be used over the intergalactic web, or through general conversation.
"YA WELL, YOU KNOW WHAT? MY PAYNUS IS BIGGER THAN YOURS!"
"your moms paynus is bigger than yours"