This is the 7985th most frequent Russian word.
константином
The word "константином" is the instrumental case of the proper noun "Константин" (Konstantin), meaning "with/by Konstantin."
Here, 'Константином' is the instrumental case of the proper noun 'Константин,' used to indicate the means by or with which an action is performed—in this case, with Konstanin.
Я познакомился с Константином вчера.
I met Konstantin yesterday.
In this sentence, 'Константином' is used as the instrumental case to signify the companion or participant in the action of discussing.
Мы обсуждали проект с Константином.
We discussed the project with Konstantin.
Here 'Константином' is indirectly referenced as part of identifying an individual, though it's not explicitly in instrumental case since 'Константин' remains nominative in this standalone verbalized identification.