We report the emission of strong coherent broadband terahertz radiation from 6H-silicon-carbide (SiC) excited with optical pulses. The measured terahertz spectral signal-to-noise ratio is better than one thousand. We determine that the terahertz radiation is generated via second order optical nonlinearity (optical rectification). We present a measurement of the ratio of nonlinear susceptibility tensor elements χzzz(2)/χzxx(2) and the complex index of refraction of silicon carbide at terahertz frequencies.