Literally: a contraction of 'Military Specification'; any item produced to satisfy written military contract specifications for that particular item.
1. 'Milspec' was long synonymous with superior design, materials, and construction, and is often still used this way.
2. In common, generally civilian, 'Milspec' is more and more often intended to mean the direct opposite: shoddy products, reflecting the growing perception that anything produce by a government contract supplier is of the lowest possible quality.
2. Man my last pair of boots lasted a whole week! Last time I buy that milspec junk!