From Understanding GIB Bid Descriptions:
Suit Quality
- biddable: 5+ cards, or 4 cards + 3 of 5 honors or more than 4 8421 points
- rebiddable: biddable + 1 card
- twice rebiddable: rebiddable + 1 card
- strong rebiddable: twice rebiddable with 4 of 5 honors or AKQ