Isomorph-free subgroup of group of prime power order

Statement
An isomorph-free subgroup of group of prime power order is a subgroup of a group where the group is a group of prime power order and the subgroup is an isomorph-free subgroup.

Weaker properties

 * Stronger than::Characteristic subgroup of group of prime power order
 * Stronger than::Normal subgroup of group of prime power order