engaged vs operant

engaged

adj
  • in contact and in operation 

  • Having the widest part of its presenting part, usually the head, enter the pelvic brim or inlet. 

  • Greatly interested. 

  • Busy or employed. 

  • attached to a wall or sunk into it halfway 

  • (of a telephone) Already involved in a telephone call when a third party calls. 

  • being attacked or attacking 

  • Having agreed to marry a particular person (one's fiancé or fiancée) or each other. 

  • Synonym of engagé (“passionately committed to a cause”) 

operant

adj
  • That operates to produce an effect. 

noun
  • Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment. 

  • An operative person or thing. 

How often have the words engaged and operant occurred in a corpus of books? (source: Google Ngram Viewer )