The use of a particular Biblical (or other scriptural) passage to prove a particular doctrine or opinion; (in extended use) the use of any text to prove a specific point.
Origin
1950s.
Definition of proof-texting in US English:
proof-texting
noun
The use of a particular Biblical (or other scriptural) passage to prove a particular doctrine or opinion; (in extended use) the use of any text to prove a specific point.