How is threat determined in Dark Heresy?

Question

In Dark Heresy, you can gain a bonus to your melee attacks if you outnumber an opponent two to one or three to one. Are opponents threatened if a player is next to them or do they have to have previously taken a combat action against that foe? (Threat does not seem to be well defined from what I've read so far.) Can a player contribute towards outnumbering a foe if they are threatened by multiple enemies at once?

I have a preference to RAW (rules as written) answers on this issue.

Answer 1

You count as being Engaged if you are within melee range of the thing in question and are in combat

and

There's nothing RAW that says you can't contribute to outnumbering one foe even if you yourself are engaged with many other foes

There's not really a hard rule as to what counts as being engaged, so we have to apply some common sense here. Basically, if you're within range of attacking or being attacked by a melee combatant, you're considered "engaged" with them, and subject to the ganging up rule.

Let's take a quick look at the rules for fleeing from combat:

Disengage (Full Action)

You break off from melee combat and may move up to your Half Move rate. Opponents whom you were engaged with do not gain the customary free attacks. p. 192

And the rules for ganging up:

Ganging Up

You have an advantage when you and your allies engage the same foe in melee combat. [...] p. 198

So we've established that you have to be in melee combat in order to benefit from the gang up rules. I propose 3 guidelines to determine if you are indeed threatening an opponent:

1. Can I smack the enemy?
2. If I were to run, would they get to smack me?
3. Is it trying to kill me?

Keep in mind that Dark Heresy is a very abstract game, so if it makes sense, run with it.