The "deniers" are dangerously absolute in their rejection of global-warming claims.
Most dangerously, many conservatives embrace the odd and self-destructive idea that authentic political heroes never compromise.
Living with a dangerously mentally ill person, a harrowing personal testimony in Wonkette.
early 13c., "difficult, arrogant, severe" (the opposite of affable), from Anglo-French dangerous, Old French dangeros (12c., Modern French dangereux), from danger (see danger).
In Chaucer, it means "hard to please, reluctant to give;" sense of "full of danger, risky" is from late 15c. Other words used in this sense included dangersome (1560s), dangerful (1540s). Related: Dangerously.