E-mail from your mom or other older relative. Momspam is almost always tasteless and/or silly, account-choking big, outdated, and sent to her whole address book. There are often multiple copies sent to you for no clear reason.
Brother: Did you get the latest momspam? The e-mail with all the pictures of "cats in angel costumes"? Two megs of junk, and she sent me seven copies!
Sister: Yeah, Mom sent it to me too, along with everyone else she knows. Consider yourself lucky that she doesn't send her Hummel pictures to you. Trust me--they're worse. Maybe getting her a PC was a mistake...
Anything that is so good it makes you want to slap your own mother (i.e., it brings you so much joy that even causing pain to your mother would not ruin it). Popularized by Bros BBQ and the “taste so good it make you wanna slap yo momma.”