participant observation - Wiktionary, the free dictionary

participant observation (uncountable)

1. (social sciences) A research methodology used in some social sciences to gain familiarity with a group of individuals and their practices through an intensive involvement, usually over an extended period of time.

• participant observer

•   participant observation on Wikipedia.Wikipedia
• “participant observation”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.