The Vietnamese word "bèo cái" refers to a type of aquatic plant known in English as "pistia" or "water lettuce." It is a floating plant that often grows in ponds, lakes, and slow-moving waters.
While "bèo cái" specifically refers to the pistia plant, "bèo" alone can also refer to various types of water plants or even be used metaphorically in some contexts, such as indicating something that is insubstantial or of little value.