Definitions of mackinaw:

• noun:   a heavy woolen cloth heavily napped and felted, often with a plaid design
• noun:   a flat-bottomed boat used on upper Great Lakes
• noun:   a thick plaid blanket formerly used in the northwestern United States
• noun:   a short plaid coat made of made of thick woolen material
• name:  A surname (very rare: popularity rank in the U.S.: #55770)