Letters that make built-in
b, l, n, t, i, u are letters that make 'built-in'
1 possible definitions for 'built-in'
Under this definition, built-in is an adjective and has the following properties:
constitutional, inbuilt, inherent, integral have the same meaning as 'built-in'
intrinsic, intrinsical are similar to 'built-in'.
"the Ptolemaic system with its built-in concept of periodicity", "a constitutional inability to tell the truth"