Definition of blister. 1  1 : a fluid-filled elevation of the epidermis â compare water blister. 2  2 : an enclosed raised spot (as in paint) resembling a blister. 3  3 : an agent (such as lewisite) that causes blistering. 4  4 : a fungal disease of plants marked by raised patches on the leaves.
One acre equals 0.0015625 square miles, 4,840 square yards, 43,560 square feet or about 4,047 square metres (0.405 hectares) (see below). While all modern variants of the acre contain 4,840 square yards, there are alternative definitions of a yard, so the exact size of an acre depends on which yard it is based.
A 1-acre plot of land is equivalent to 43,560 square feet or 4,840 square yards. An acre is also equal to about 75 percent of the size of a football field.