Ignorant;
uninformed;
witless;
clueless; wallowing in
nescience.
I don't even know how to pronounce it.
Is it NEE- or NESS-? Or NESH-? Is the middle sibilant S as in science or SH as in conscience? And how many syllables: do you make the –I- separate as in omniscient or silent as in conscience?
[From the Latin nescius, from negative ne- and the root sci- 'to know'. This also gave the Old French word nice, borrowed into English with that same meaning 'ignorant'.]