To make or become harsh, rough, or severe; to increase in harshness or severity.
From 'harsh' (Germanic origin, related to Old Norse 'harðr' meaning hard) plus the suffix '-en' which makes adjectives into verbs meaning 'to become' or 'to make.' This is a relatively modern formation following standard English verb-making patterns.
English speakers often add '-en' to adjectives to turn them into verbs (like 'darken,' 'lighten,' 'soften'), and this pattern lets us describe how weather, voices, or even laws can become harsher over time.
Complete word intelligence in one call. Free tier — 50 lookups/day.