- full of danger or risk; causing danger; perilous; risky; hazardous; unsafe.
- able or likely to cause physical injury: a dangerous criminal.
- causing danger; perilous
adj.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. see little knowledge is a dangerous thing; live dangerously.