From BiblePortal Wikipedia

Morrish Bible Dictionary [1]

A well in the valley of Gerar, dug by the servants of Isaac, and striven for by the servants of Abimelech; hence its name, which signifies 'strife.'  Genesis 26:20 .

Smith's Bible Dictionary [2]

E'sek. (Contention). A well which the herdsmen of Isaac dug in the valley of Gerar.  Genesis 26:20.

Hastings' Dictionary of the Bible [3]

ESEK (‘contention,’   Genesis 26:20 ). A well dug by Isaac in the region near Rehoboth and Gerar. The site is unknown.

Fausset's Bible Dictionary [4]

("calumny, wrong".) A well dug by Isaac's men, but abandoned when the men of Gerar strove for it ( Genesis 26:20).

Holman Bible Dictionary [5]

 Genesis 26:18-22

Easton's Bible Dictionary [6]

 Genesis 26:20

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [7]

(Hebrew id. עֵשֶׂק , Quarrel; Sept. and Vulg. translate Ἀδικία , Calumnia, as if reading עשֶׁק ), a well ( בְּאֵר ) containing a spring of water, which the herdsmen of Isaac dug in the valley of Gerar, and which received its name because the herdmen of Gerar quarreled הַתְעִשְׁקוּ , Wrangled, Sept. Ἠδίκησαν , Vulg. evasively, A.V. "strove;" but different from the וִיָּרַיבוּ of the preceding clause, Ἐμαχήσαντο , Jurgiun Fuit, "strove") with him for the possession of it ( Genesis 26:20). Isaac seems to have therefore relinquished it. It appears not to have been one of those which Abraham had previously dug ( Genesis 26:18; the contest there was a question of title, here of possession). There are still several wells in this vicinity. (See Gerar).

International Standard Bible Encyclopedia [8]

ē´sek ( עשׂק , ‛ēseḳ  ; Septuagint Ἀδικία , Adikı́a ): The name given by Isaac to a well dug by his servants, for the use of which the herdsmen of Gerar strove with them - "contention" ( Genesis 26:20 ). It lay in the neighborhood of Rehoboth and Gerar: but the site is not identified.