paraquat par·a·quat (pār'ə-kwŏt')
A colorless compound or a related yellow compound used as a herbicide.
A toxic compound used as a herbicide, especially in its colorless, dichloride form (C12H14Cl2N2) or in its yellow, bismethyl sulfate form (C14H20N2O8S2). Paraquat is used primarily to control grass and weeds. Its use in the United States is restricted because of its high level of toxicity.