Final answer:
The technique used in the phrase 'they fought like cats and dogs' is known as simile. This is because it directly compares two different subjects using 'like' or 'as'.
Step-by-step explanation:
The phrase 'they fought like cats and dogs' is a perfect example of simile which is one among the various figurative language techniques. A simile is a figure of speech that introduces an explicit comparison between two different things using the word 'like' or 'as'. In this case, the comparison is being made with the familiar notion of cats and dogs being at odds, symbolizing a fierce conflict or a fight.
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