A type of wank that is performed in anticipation of an iminant sexual encounter. By having a tactical wank, you save your self from busting quick when your iminant sexual encounter occurs.
Johnny: What are you up to?
TJ: Just about to have a tactical wank,I've got a tinder bitch coming over tonight.
A tactical wank is one where you manage to slip away in an awkward or boring situation to masturbate in a quick time frame and manage to get back without anyone noticing that you had gone away. Further more people must not have knowledge of what has just taken place. A more informal slang term for this is "tac wank"
Example 1.
*R slips back hoping no one has notices his absence*
"Dude, we know that look, you have just been for a tactical wank haven't you."
Example 2.
"Where have you been son, we were having an important dinner discussion about poor university grades?"