half track: a motor vehicle propelled by half tracks; frequently used by the military
tracked vehicle: a self-propelled vehicle that moves on tracks
gram's method: a staining technique used to classify bacteria; bacteria are stained with gentian violet and then treated with Gram's solution; after being decolorized with alcohol and treated with safranine and washed in water, those that retain the gentian violet are Gram-positive and those that do not retain it are Gram-negative