Gad n.
 1. The point of a spear, or an arrowhead.
 2. A pointed or wedge-shaped instrument of metal, as a steel wedge used in mining, etc.
 I will go get a leaf of brass,
 And with a gad of steel will write these words.   --Shak.
 3. A sharp-pointed rod; a goad.
 4. A spike on a gauntlet; a gadling.
 5. A wedge-shaped billet of iron or steel. [Obs.]
    Flemish steel . . . some in bars and some in gads.   --Moxon.
 6. A rod or stick, as a fishing rod, a measuring rod, or a rod used to drive cattle with. [Prov. Eng. Local, U.S.]
 Upon the gad, upon the spur of the moment; hastily. [Obs.] “All this done upon the gad!”