What is the "fine art term" for office printer as medium?
Chris H's comment is the answer in a nutshell: the description should include the medium, and depends on the type of printing. If it's an inkjet print, you can state that; if it's a laser print, the artwork's description could say so. You can also just say 'digital print', combining all digital printing possibilities.

Often the type of paper - if exceptional or otherwise deemed important for the artwork - is also included in the description (e.g. 'giclée print on 210 gr Hahnemuhle Albrecht Durer paper'). 

Ultimately, though, you describe the print in as much detail as you think is right towards your audience or clients. In some instances you could even be emphatically vague about it if you think it accentuates (the concept of) a particular artwork.
The 'office' in 'office printer' doesn't matter for the technology used, as far as it concerns the quality of the prints, but if you think that fact is important for understanding your piece, it's completely fine to include that.



You can also have a look here and here to see what terminology is used (which also includes vague terms like 'pigment' and 'photo print').