[Apollo81]

This is from a robot MP duplicate. None vulnerable.

♠Kx
♥x
♦AJTxx
♣AKJxx

1♦-(2♦)-p-(2♥)
3♣-(p)-3♠-(Dbl)
??

[G_R__E_G]

Any idea what GIB claimed the 3♠ bid meant?

[Apollo81]

I don't think the description of any of the previous bids or bids under consideration was helpful.

[Jlall]

Pass and see what gib is up to.

[Apollo81]

GIBpard had Jxx xxx Qxx Qxxx or some such. Here are the results:

If you bid 4♣, GIB passes and you play 4♣ making for about 80%

If you bid 4♦, GIB corrects to 5♣ and you're down 1 for about 46%

If you pass (like I did), GIB leaps to 6♣ (doubled), down 2 for about 15%

I didn't see any redoublers in the field. Who knows what would happen -- maybe GIB would bid 7♣.

[PetteriLem]

I guess it became obvious, but GIB thinks that 3♣ shows a huge hand. It will always go for a slam with 4-6 pointer (queens and jacks doesnt matter) without any feature or good fit. Why it does so is hard to imagine. More experience allowes you avoid some traps that GIB sets for you.
As a side issue try to avoid this sequenze. I have tried it twice, just to make sure. 1♠ - 4NT; 5NT (showes void) - ?. Any cue bid will be passed, despite bid info claims it to be forcing and showes ace in the suit.