Can be translated as "precious" or "wholesome." It's meant to describe precious or wholesome moments, which are usually interactions between two or more VTubers. This originated from another word, 尊い (toutoi). This variation may have started from a Nijisanji fan comic back in 2018. Can also be used as ていてい (teitei), tee-tee, or tete.
▸ "Last night's OkaKoro stream was incredibly teetee."
▸ "That's very teetee of you and her."
▸ "Honestly, we can't stop finding teetee clips of Crossick."