Definitions of gulp:

• noun:   a large and hurried swallow

  Example: "He finished it at a single gulp"

• noun:   a spasmodic reflex of the throat made as if in swallowing
• verb:   utter or make a noise, as when swallowing too quickly

  Example: "He gulped for help after choking on a big piece of meat"

• verb:   to swallow hurriedly or greedily or in one draught

  Example: "The men gulped down their beers"