sun spider Syllabification: (sun spi·der)Definition of sun spider noun a fast-moving predatory arachnid with a pair of massive vertical pincers (chelicerae). Sun spiders live chiefly in warm deserts, many are active by day, and some grow to a large size. Order Solifugae (or Solpugida) sun spider in other Oxford dictionaries Definition of sun spider in the British & World English dictionary