A blunt is a cigar which is wider than a cigarillo and not quite as wide as a traditional cigar. Blunts usually consist of two main parts; the inner leaf, which is similar to a cigarette rolling paper, except it is made of tobacco, and a thicker outer leaf which is rolled around the inner leaf in a spiral. In most commercially available blunts, the "leaves" are not actual tobacco leaves but rather paper made from tobacco pulp.
Blunts get their name from their 'broad or rounded tip', and were named as such in the 1800s to differentiate them from other cigars with a tapered, pointed tip.
Many marijuana smokers use a blunt to smoke marijuana by cutting it in the middle (from the part you light up to the part you smoke from), hollowing it out and filling it up with weed.