Noun
A Hebrew stringed instrument.
(mathematical analysis) The symbol ∇, used to denote the gradient operator.
Source: en.wiktionary.orgDifferential operations main Vector calculus studies various differential operators defined on scalar or vector fields, which are typically expressed in terms of the del operator ( ), also known as "nabla". Source: Internet
His 1867 Elementary Treatise of Quaternions included extensive treatment of the nabla or del operator ∇. Source: Internet