a nodding acquaintance

A very limited knowledge of or familiarity with a given person or thing. I'll help you as best I can, but I only have a nodding acquaintance with property laws. I have a nodding acquaintance with him, but I wouldn't feel comfortable asking him to help me on this project. Ruth and I had only a nodding acquaintance before going to the party, but once we got talking, it was like we'd been friends our whole lives.

a nodding acquaintance with (someone or something)

A very limited knowledge of or familiarity with a given person or thing. I'll help you as best I can, but I only have a nodding acquaintance with property laws. I have a nodding acquaintance with him, but I wouldn't feel comfortable asking him to help me on this project. Jim asked me to help fix his computer for him, but I'm afraid I only have a nodding acquaintance with how his machine works.