Adj. Originally a term that means fields that are not being use for crops. Current usage means unproductive.
She's going through a fallow period.
(v.) To plow, but not to seed.
Plow, meaning to have sex
Seed, meaning the female egg and sperm joining.
"Shit man...good job I only fallowed her."
"Dude, I'd fallow that girl."
Man1: "What the fuck dude! I thought you were only going to fallow her! not make babies"
Man2: "shit man, I know. I got knocked up."