If there is a fight going on that their group or their friends or maybe just friendlies (IE, a rogue sitting watching an outcast v corsair fight) are involved in, then they could simply be designating a target that they are going to attack.
Eg.
well i was out pirating in liberty and an lsf came up and we RP'd. about 55 seconds into the battle a navy comes on my scanners and says engaging outcast and nothing else so i disengaged cause my trident couldnt fight a cruiser. and that's about it.
I would say that it's acceptable if you were joining a fight if it's just started and you're in a group with the person(s) already engaged. Otherwise, you're gonna want some RP first. But don't quote me on that.
Yeah if you are fighting a person in a group? expect the others to pop in at anytime,with very little RP chat.
Not in a group? Then that would not be enough according to rules. Problem is? trying to prove it. It has happened to me several times in last few week's,and i reported,and admins do nothing. To hard to prove.
Hell i went from 1 on 1 to 6 on 1 with not a single word other day.
//A solution would be moving out of liberty to basically anywhere else; you can be sure 90% of the time a one manned cruiser wont engage you like that.//
If X pilot requests assistance to Y pilot or nearby lawful then shouting assisting could be considered acceptable, most RP pilots wont request a cruiser to assist him anyways but still.
You can also type in local and tell the cruiser to disengage; probably that wont help but you can always take pics and report it and se what the admins have to say.