unfamiliar
adj.adj. describing something you do not know or recognize. You use this when you see or hear something for the first time.
adj. not known or recognized; not having knowledge or experience of a particular subject or place.
The city felt strange because the streets were unfamiliar.
She felt nervous walking through the unfamiliar neighborhood at night without a map.
The researcher struggled to interpret the data because the software used an unfamiliar algorithm that differed significantly from industry standards.
From un- + familiar.
Often followed by the preposition 'with' when describing a person's lack of knowledge.
I am unfamiliar of this systemI am unfamiliar with this systemWhen describing a lack of knowledge, the adjective takes the preposition 'with' rather than 'of'.