Lewis base

noun, Chemistry
1.
any substance capable of forming a covalent bond with an acid by transferring a pair of electrons to it.
Origin
1960-65; named after G. N. Lewis
British Dictionary definitions for Lewis base

Lewis base

noun
1.
a substance capable of donating a pair of electrons to an acid to form a covalent bond Compare Lewis acid
Word Origin
C20: named after G. N. Lewis (1875–1946), US chemist