ˈ ̷ ̷tə(r)dlē, -li adjective
Etymology: bastard (I) + -ly
1. : of no worth or value : contemptible , mean — usually a generalized term of abuse
quarts of that bastardly stuff — Calder Willingham
I'm not just doing it to be bastardly — James Jones
2. obsolete : of no authority : spurious , corrupt
apocryphal and bastardly canons which they father upon the Apostles — John Donne