English▸ adjective able or likely to cause harm or injury:
a dangerous animal
insecticides which are dangerous to the environment.
▪ likely to cause problems or to have adverse consequences:
it is dangerous to convict on his evidence.
– ORIGIN Middle English (in the senses ‘arrogant’, ‘fastidious’, and ‘difficult to please’): from Old French dangereus, from dangier (see danger).