Meaning of “criminal” - Learner’s Dictionary

criminal

noun [ C ] us uk /ˈkrɪmɪnəl/
a notorious criminala convicted criminalhardened criminalsThey've been unfairly labelled as criminals.They've introduced a revolutionary new programme to reform criminals.

B1 someone who has committed a crime:

a dangerous/violent criminal

(Definition of “criminal noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)