  By replacing the Euler gamma function by the Barnes double gamma function in
the definition of the Meijer $G$-function, we introduce a new family of special
functions, which we call $K$-functions. This is a very general class of
functions, which includes as special cases Meijer $G$-functions (thus also all
hypergeometric functions ${}_p F_q$) as well as several new functions that
appeared recently in the literature. Our goal is to define the $K$-function,
study its analytic and transformation properties and relate it to several
functions that appeared recently in the study of random processes and the
fractional Laplacian. We further introduce a generalization of the Kilbas-Saigo
function and show that it is a special case of $K$-function.
