The term operational definition is almost entirely associated with quantitative research, where it describes how one measures ("operationalizes") something. The closest equivalent I can think of in qualitative research is to define eligibility criteria for determining who you will interview.

In semi-structured interviewing, the most important issue is often what a particular idea means to your participants, rather than what it means to you. When it is necessary to specify a definition for something you want them to discuss, then you simply do so.

The term operational definition is almost entirely associated with quantitative research, where it describes how one measures ("operationalizes") something. The closest equivalent I can think of in qualitative research is to define eligibility criteria for determining who you will interview.

In semi-structured interviewing, the most important issue is often what a particular idea means to your participants, rather than what it means to you. When it is necessary to specify a definition for something you want them to discuss, then you simply do so.

The operational definition contains dimensions and indicators of the concept. I think we call them indicators because they indicate the small parts of the concept that could be directly identified or measured. If you identify or measure those small parts you identify or measure the concept (the concept is too abstract to be identified or measured directly).

We use operational definition when we identify or measure concepts with structured instruments like questionnaires or structured interview guides. We use indicators to formulate the questions. Every indicator in an operational definition is identified or measured with a question.

For exemple if an indicator of religiosity is going to the church then you use it in your data collecting instrument like this: you ask your subjects if they go to the church.

In a semistructured interview I think you ask a question like that for every indicator you have in your operational definition and you also leave your subjects the liberty to describe any other indicator of their religiosity they feel like you missed.

It depends on different views and opinions of others in addition to the objectives of the study itself.