1. unusual or unexpected
the idea/remark/problem came out of left field
This expression is used to refer to something that is untypical or surprising, especially with regards to its source, with 'left field' being the metaphorical origin of something unusual. The surprise factor involved means that things coming 'out of left field' are often very difficult to plan for, deal with, or properly understand. However, its connotations are not all negative. Sometimes a brilliant idea or moment of inspiration can come in this way. It is used in both a social and professional context, and is similar to the term 'out of the blue.'