Full Idea
A propositional logic set of sentences Γ is 'satisfiable' if there is at least one admissible truth-assignment that makes all of its sentences true.
Gist of Idea
A sentence-set is 'satisfiable' if at least one truth-assignment makes them all true
Source
José L. Zalabardo (Introduction to the Theory of Logic [2000], §2.4)
Book Reference
Zalabardo,José L.: 'Introduction to the Theory of Logic' [Westview 2000], p.53