This mutation is triggered when the J'avo suffers heavy damage to the head. The creature spits a sticky, viscous fluid akin to webbing to constrain the player that can leave them vulnerable to other attacks whilst they try to free themselves.
While the player is freeing themselves from the Glava-Sluz' webbing, it begins to use melee moves until you free yourself, in which it tries to spit more acid webbing.
To kill this particular creature, the player can either use melee moves constantly or the crossbow (If you are using Ada's campaign and you need to be undetected: i.e. preventing using guns), a knife (Chris Redfield), or a shotgun to the head 3 times (Leon).