The term 'tsunami relative' can be summarized by the crossword solution 'EAGRE, ' which is a five-letter word. An EAGRE is a tidal bore, which is a large wave that is created when the tide rushes into a river or estuary. It is related to a tsunami in that both are caused by large bodies of water, but an EAGRE is much smaller and usually occurs in rivers and estuaries, while a tsunami is much larger and occurs in oceans.