1 (abbreviation R.) a natural flow of water that continues in a long line across land to the sea/ocean:
the River Thames * the Hudson River * the river bank (= the ground at the side of a river) * to travel up / down river (= in the opposite direction to / in the same direction as the way in which the river is flowing) * the mouth of the river (= where it enters the sea / ocean) * a houseboat on the river * They have a house on the river (= beside it).
2 ~ (of sth) a large amount of liquid that is flowing in a particular direction:
Rivers of molten lava flowed down the mountain.
IDIOMS see SELLv.
