A naked option strategy is an unhedged strategy making exclusive use of either a short call strategy (selling or writing call options), or a short put strategy (selling or writing put options). These positions are called naked strategies because they do not involve an offsetting or risk-reducing position in another option or in the underlying security. 
A short call position is uncovered if the writer does not have a long stock or long call position. A short put position is uncovered if the writer is not short stock or long another put.
It is the antithesis of a covered option.