A thick, pale, mayonnaise-like sauce of vegetable oil, egg yolk, vinegar and a little sugar; brands also sell a distinctly sweet version. It dresses potato and vegetable salads and goes into sandwiches.
沙拉 transliterates 'salad'. In mainland Chinese supermarkets, 沙拉酱 most often refers to a sweet, mayo-like dressing (think Kewpie style) rather than vinaigrette. For pure mayo, 蛋黄酱 is more precise.