1. most sudden and unexpected; happening without warning (superlative form of abrupt)
2. most rudely brief in speech or manner; most curt (superlative form of abrupt)
3. most steep or sharply angled (superlative form of abrupt)

Examples

• The mountain trail took the abruptest turn at the cliff edge.
• His abruptest response came when asked about his resignation.
• The stock market’s abruptest decline occurred during the crash.
• She gave her abruptest reply and walked away.
• The abruptest change in weather caught everyone off guard.
• The cliff face showed the abruptest drop into the valley.
• His abruptest manner appeared when he was stressed.