1. in a way that causes fear or alarm
2. to an extreme or alarming degree
Usage: used for emphasis

Examples

• The dog barked frighteningly loud in the middle of the night.
• The test was frighteningly difficult for most students.
• She drove frighteningly fast down the winding mountain road.
• The storm clouds gathered frighteningly quickly overhead.
• The cost of college tuition has risen frighteningly high.
• His fever spiked to a frighteningly dangerous level.
• The building swayed frighteningly during the earthquake.