The exsecant,[2][3][4][5][6][7][8][9] (Latin: secans exterior[10][11][12][13]) also known as exterior, external,[14][15][16][17] outward or outer secant and abbreviated as exsec[18][19][20][21] or exs,[22] is a trigonometric function defined in terms of the secant function sec(θ):[23]