suicidal UK /ˌsuː.ɪˈsaɪ.dəl/US /ˌsu.əˈsaɪ.dəl/adjective 4noun 1forms 3 adjective4 •Pertaining to suicide.He is an authority on the precursors of suicidal behavior. •Of a person, likely to commit, or to attempt to commit, suicide.After losing his job, his wife, and his leg in a single week, he became suicidal. •Of a voluntarily-chosen course of action, highly likely to certain to result in the deaths of the participants; dangerous or reckless to such a degree as to be tantamount to suicide for those taking part. •(informal) Extremely reckless.His driving habits are utterly suicidal. noun1 •Someone suicidal; someone likely to kill themselves. formssuicidals · more suicidal · most suicidal