When an older person subtly flirts with an underage member of the opposite sex to keep he/she interested until the underage person is of age and ready to play in the big leagues.
Example 1:
Rick: "Dude, how did you hook up with John's little sister? She was jail bait two days ago!"
Greyson: "Had her on the farm team for 3 years"
Example 2:
Ted: "Man, why is that fat girl on your farm team?"
Barney: "She just joined the volleyball team, in 4 years she'll probably be skinny"