Join of finitely many 2-subnormal subgroups

Definition
A subgroup of a group is termed a join of finitely many 2-subnormal subgroups if it is expressible as the join (i.e., the subgroup generated) of finitely many 2-subnormal subgroups of the whole group.

Stronger properties

 * Weaker than::2-subnormal subgroup
 * Weaker than::Normal subgroup

Weaker properties

 * Stronger than::Join-transitively subnormal subgroup
 * Stronger than::Subnormal subgroup