Sentence:  Thus, a Gaussian shape for the <WSD>microstrain</WSD>-broadened diffraction-line profile occurs for a Gaussian <WSD>microstrain</WSD> distribution. 
Meaning of the word marked with <WSD> tags:  The root mean square of the variations in the lattice parameters across the individual crystallites, usually across microscopic distances, <ϵ2>1/2. By definition, it cannot be negative. In contrast, macrostrain refers to the overall change in the lattice parameters caused by a composition change or temperature change or pressure change.