"Unknown" refers to something that is not known or familiar. It represents a lack of knowledge or understanding about a particular thing or person. Full definition
But there is always the possibility of unknown sources of error, but methods for accounting for those are somewhat unclear. (realclimate.org)
Others are still relatively unknown in the world of modern baby names. (thestir.cafemom.com)
The pricing of the device is still unknown of course, we'll have to wait for the official announcement or some additional unofficial info. (androidheadlines.com)