Magnetic microwave parametric excitation of magnetoelastic waves in the easy-plane antiferromagnet FeBO3 is studied at room temperature. Measurements were performed at X-band with a perpendicular pumping configuration. We observed the saturation of the microwave absorption of antiferromagnetic resonance above the pumping threshold and simultaneous microwave radiation from the sample at half pump frequency. The radiation spectrum, its intensity dependence on the pumping power and magnetic field are investigated. The obtained results are in agreement with the fact that the radiation appears due to parametrically excited transverse quasiphonons propagating along the "hard" magnetic axis of a crystal.