To contain or confine someone or something in a pen or something that functions like a pen. I managed to pen in the piglets before they got away.Just make sure the kids are penned in out back and let them play amongst themselves.
pen (someone or an animal) in (some place)
to confine someone or an animal in a pen. We penned all the kids in out in the backyard while we got the party things ready in the house.We had to pen in the kids to keep them away from the traffic.Alice penned her dog in.
pen in
v.
To confine someone or something in or as if in a pen: The farmer penned the pigs in for the night. If you don't pen in the chickens, the wolves will get them.