Dictionary.com
Thesaurus.com

instructor vs. lecturer

[in-struhk-ter] / ɪnˈstrʌk tər /

noun

  1. a person who instructs; teacher.

    Synonyms:
    pedagogue, preceptor, schoolmaster, tutor
  2. a teacher in a college or university who ranks below an assistant professor.

[lek-cher-er] / ˈlɛk tʃər ər /

noun

  1. a person who lectures.

  2. an academic rank given in colleges and universities to a teacher ranking below assistant professor.