  We present a comprehensive x-ray scattering study of spontaneous
magnetostriction in hexagonal MnTe, an antiferromagnetic semiconductor with a
Neel temperature of $T_{\mathrm{N}} = 307$ K. We observe the largest
spontaneous magnetovolume effect known for an antiferromagnet, reaching a
volume contraction of $|\Delta V/V| > 7 \times 10^{-3}$. This can be justified
semiquantitatively by considering bulk material properties, the spatial
dependence of the superexchange interaction, and the geometrical arrangement of
magnetic moments in MnTe. The highly unusual linear scaling of the
magnetovolume effect with the short-range magnetic correlations, beginning in
the paramagnetic state well above $T_{\mathrm{N}}$, points to a novel physical
mechanism, which we explain in terms of a trilinear coupling of the elastic
strain with superposed distinct domains of the antiferromagnetic order
parameter. This novel mechanism for coupling lattice strain to robust
short-range magnetic order casts new light on magnetostrictive phenomena and
also provides a template by which the exceptional magnetostrictive properties
of MnTe might be realized in a wide range of other functional materials.
