Having the quality or appearance of being extremely large, like a giant; enormous and impressive in size.
From 'giant' combined with the suffix '-esque', which comes from Italian and means 'in the manner of' or 'having the quality of'. This created the English descriptive adjective in the 16th-17th centuries.
The suffix '-esque' is super productive in English—once you know it means 'like or in the style of,' you can actually apply it to tons of words to create new meanings, which is exactly what happened with giantesque!
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