The superlative form of 'cross', meaning most angry, irritable, or in a bad mood.
From 'cross' (irritable, angry), an adjective derived from unclear origins (possibly from Old Norse), with the superlative suffix '-est' added to create the most extreme form.
The word 'cross' meaning 'angry' is actually quite old, but it's fading from American English while staying strong in British speech—watching words die out in some regions while persisting in others shows how English is splitting into different varieties right before our eyes.
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