1. To fall behind:
* Antonyms: Catch up, keep pace, stay together, maintain formation
2. To spread out in a disorderly way:
* Antonyms: Cluster, gather, assemble, group, align, organize, consolidate
3. To grow in a weak or irregular way:
* Antonyms: Thrive, flourish, prosper, grow strong, develop well
So, choose the antonym that best fits the specific meaning of "straggle" in your context.