  The D-term is one of the conserved charges of hadrons defined as the forward
limit of the gravitational form factor $D(t)$. We calculate the nucleon's
D-term in a holographic QCD model in which the nucleon is described as a
soliton in five dimensions. We show that the form factor $D(t)$ is saturated by
the exchanges of infinitely many $0^{++}$ and $2^{++}$ glueballs dual to
transverse-traceless metric fluctuations on the Wick rotated AdS$_7$ black hole
geometry. We refer to this phenomenon as `glueball dominance', in perfect
analogy to the vector meson dominance of the electromagnetic form factors.
However, the value at vanishing momentum transfer $D(t=0)$ can be interpreted
as due to the exchange of pairs of pions and infinitely many vector and
axial-vector mesons without any reference to glueballs. We find that the D-term
is slightly negative as a result of a cancellation between the isovector and
isoscalar meson contributions.
