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!”