Longman Dictionary of Contemporary English - roar

~1 v 1 to make a deep, very loud noise  (We heard a lion roar.) 2 to say or shout something in a deep, powerful voice  ("Get out of my house!" he roared.) 3 also roar with laughter especially BrE to laugh loudly and continuously  (When Charlie's trousers fell down, the audience roared.) 4 if a vehicle roars somewhere, it moves very quickly and noisily + past/down etc  (There was a cloud of dust as a truck roared past.) ~2 n 1 a deep, loud noise made by an animal such as a lion, or by someone's voice  (A roar of approval came from the crowd.) 2 a continuous loud noise, especially made by a machine or a strong wind  (the roar of the traffic)