Gabbatha = "elevated or a platform"
1) a raised place, elevation. In the Greek was called Lithostrotos, or the pavement of stones, as the Syrian version renders it: it is thought to be the room Gazith, in which the Sanhedrin sat in the temple when they tried capital causes; and it was so called, because it was paved with smooth, square hewn stones: "it was in the north part; half of it was holy, and half of it was common: and it had two doors, one for that part which was holy, and another for that part that was common; and in that half that was common the sanhedrin sat." So that into this part of it, and by this door, Pilate, though a Gentile, might enter. This place, in the language of the Jews, who at that time spoke Syrian, was Gabbatha, from its height, as it should seem; though the Syrian and Persian versions read Gaphiphtha, which signifies a fence or enclosure. Mention is made in the Talmud of the upper Gab in the mountain of the house; but whether the same with this Gabbatha, and whether this is the same with the chamber Gazith, is not certain. The Septuagint uses the same word as John here does, and calls by the same name the pavement of the temple on which Israelites fell and worshipped God. (2Ch 7:3) (Gill) The Hebrew word for Pavement occurs only once in the Old Testament. In 2Ki 16:17 we read, "King Ahaz cut off the borders of the bases, and removed the laver from off them; and took down the sea from off the brazen oxen that were under it, and put it upon the pavement of stones." In Ahaz's case his act was the conclusive token of his abject apostasy. So here of Pilate coming down to the apostate Jews. In the former case it was a Jewish ruler dominated by a Gentile idolater; in the latter, a Gentile idolater dominated by Jews who had rejected the Messiah! (AWP Joh 19:13)
Part of Speech: noun proper locative
Of Chaldee origin (compare [H1355]); the knoll; gabbatha, a vernacular term for the Roman tribunal in Jerusalem: - Gabbatha.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root Γαββαθα; click on the second column to search for that grammatical form of the root Γαββαθα; click on the third column to search for that word and grammatical form; click on the total to search for the root Γαββαθα.