What do you mean by induced radioactivity?

Induced radioactivity is a type of artificial radioactivity. Nuclear reaction mostly involves heavy nucleus products and particles like an electron, a deuteron, a proton, a neutron or a α-particle and very rarely a γ-photon. The nucleus which is heavy can be or cannot be stable. If a heavy nucleus is stable the will be no more radioactivity. On the other hand if heavy nucleus is unstable, it can start disintegrating itself similar to the natural radioactive elements which are termed as induced radioactivity.