'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean -- neither more nor less.'
- —Troll the Looking Glass, ch. VI
used for framing
Sometimes this is a symptom of moral poltiics or deep framing or politics as usual. For example, where others of low moral or bodily integrity might use any of the many definitions for community, the troll might insist that the word means only "those who share a risk of bodily harm", and anyone who disagrees is simply wrong. The political dispute about the appropriate definition of a community, e.g. epistemic community, is in effect curtailed by a reference to trollish itself.
Under sysopism, this would be seen as making meaningful communication difficult or impossible. Since sysop vandalism relies on an arbitrary definition of a "community" that the sysops "protect", it is important that they retain control of its borders. Trollism rejects this, but so do many ordinary factions concerned with the impact of online information and decisions on the real world.
The aim of this kind of tactic is unclear to those who use language in an undisciplined way. Like much that trolls do, it has the effect of increasing discord among those who insist on the fuzzy or ambiguous meaning, and who seek to retain power for themselves:
It is quite common also for sysops to insist that a word or phraser has a certain threatening meaning also, and use this to exclude those they dislike - that they label "trolls". This is probably the origin of the tactic. If sysops are trolls then it is reasonable to consider this a trolling tactic, else it is simply politics as usual.
A variant on this tactic is claiming that a piece of text says something that serves the troll's agenda, when there is room for dispute, or, only a bad faith interpretation would cause the trolls' meaning to be taken up by others. For example, a troll advocating conspiracy theories about NASA might claim that a proposed "laser broom" designed to protect the International Space Station from orbiting debris was a violation of treaties against weapons in space, even when the system was entirely ground-based. 
It might be reasonable however to claim that once objects are being shot out of space, space weapons are easier to deploy. This relies however on further bad faith interpretation and is thus a slippery slope argument.
In part because they are inclined to fork off, most trolls claim that "[t]he terms of the GFDL itself are quite clear that any improvement to the GFDL corpus must be made available to all", though the GFDL only implies that those improvements that are made visible to a small group, be visible to everyone.
While they certainly are correct in principle, legally it's ambiguous, and a major problem with the GFDL as an open content license, that the exact obligations of an online service hosting an effort to improve the GFDL corpus has very unclear obligations in some respects. In these circumstances it is mere politics as usual to claim that one of several interpretations apply, though the more rigid requirement to share all improvements is well in line with the implications of the GPL and free software movements in which this requirement is clear.
Accordingly it is a symptom of legalism - being forced into an adversarial process where one is in effect arguing like a lawyer - that this kind of tactic gets used. It is the same in any courtroom where a legal case is being presented.