cornerstone meaning and definition

CORNERSTONE noun

Definition of cornerstone (noun)

1. the fundamental assumptions from which something is begun or developed or calculated or explained
   • "the whole argument rested on a basis of conjecture"
   • synonyms: base, basis, foundation, fundament, groundwork
2. a stone in the exterior of a large and important building; usually carved with a date and laid with appropriate ceremonies
3. a stone at the outer corner of two intersecting masonry walls