You win.
[QUOTE=dictionary.com]
sig·nif·i·cant (sĭg-nĭf’ĭ-kənt)
adj.
- Having or expressing a meaning; meaningful.
- Having or expressing a covert meaning; suggestive: a significant glance. See Synonyms at expressive.
- Having or likely to have a major effect; important: a significant change in the tax laws.
- Fairly large in amount or quantity: significant casualties; no significant opposition.
- Statistics Of or relating to observations or occurrences that are too closely correlated to be attributed to chance and therefore indicate a systematic relationship.
[/QUOTE]
1 & 2 are quite subjective as meaningfulness is determined by the given person. 3-5, however, are objective in an increasing order.
“Shifted the course significantly” is probably usage 3 or 4. It may not in the end prevent a collision, but at least it was likely to have done as to, for example, merit a recalculation of the trajectory.
Re: the cave, some of you here are using the word in its subjective sense, whereas the official probably isn’t. In making a decision like this they tend to try to be seen as being objective. I don’t think your disagreement is with their use of the word, but rather the reasoning they followed when assessing the likely impact.
…what? I thought fun is not allowed in the Pit.
I could care less about this entire thread, irregardless of the significant objective opinions exposed thereof.
Well at least you care a little. That’s significant.
Yes, this writer thinks that’s the consensus of opinion at this time.
The consensus isn’t of any consequence as long as people continue to inflate the significance of this thread by posting in it. 
I predict consequences. Many significant consequences.