The term 'billows' can be defined as a large mass of something that is moving or rising and falling in waves. It is often used to describe clouds, smoke, or water. The two crossword solutions for the term 'billows' are 'heaves' and 'surges'. 'Heaves' is a verb meaning to move or rise and fall in waves, while 'surges' is a noun meaning a sudden strong flow or increase. Both words are used to describe the same phenomenon, but from different perspectives.