In a very bad or unpleasant way, or used as an intensifier meaning 'extremely.'
From Latin terribilis 'causing terror,' from terrere 'to frighten.' The word underwent semantic bleaching, evolving from meaning 'in a terror-inducing way' to simply 'very' by the 18th century.
This word perfectly demonstrates how language softens over time - what once meant 'in a way that causes terror' now casually intensifies positive statements like 'terribly excited.' It's linguistic inflation at work, where strong words gradually lose their punch.
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