What unique physical characteristic distinguishes a spider with long front legs and short back legs from other arachnids?

The unique physical characteristic that distinguishes a spider with long front legs and short back legs from other arachnids is its distinctive body shape, known as the "crab-like" or "crab spider" morphology. This body shape allows these Spiders to move sideways with agility, unlike other arachnids that typically move in a forward direction.