Join-transitively 2-subnormal subgroup

Symbol-free definition
A subgroup of a group is termed join-transitively 2-subnormal if its join with any defining ingredient::2-subnormal subgroup is 2-subnormal.

Note that this is strictly stronger than the property of being 2-subnormal, because 2-subnormality is not finite-join-closed.

Stronger properties

 * Weaker than::Normal subgroup:

Weaker properties

 * Stronger than::2-subnormal subgroup: Also related:
 * Stronger than::Join-transitively subnormal subgroup
 * Stronger than::Subnormal subgroup