Aschbacher block

In mathematical finite group theory, a block, sometimes called Aschbacher block, is a subgroup giving an obstruction to Thompson factorization and pushing up. Blocks were introduced by Michael Aschbacher.
Definition.
A group "L" is called short if it has the following properties :
An example of a short group is the semidirect product of a quasisimple group with an irreducible module over the 2-element field F2
A block of a group "G" is a short subnormal subgroup.