What do you mean by the term decrepitation?

Decrepitation:

• The noise is produced when certain chemical compounds are heated, or it refers to the cracking, or breaking-up of lumps of limestone during heating.
• Sometimes a compound on heating produces a crackling sound.
• It is known as decrepitation.
• For example, Lead nitrate($\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2$) upon heating produces lead oxide, nitrogen dioxide, and oxygen gas along with a crackling sound, called decrepitation.
• $\underset{\mathrm{Lead}\mathrm{Nitrate}}{2\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{s}\right)}\stackrel{∆}{\to }\underset{\mathrm{Lead}\mathrm{Oxide}}{2\mathrm{PbO}\left(\mathrm{s}\right)}+\underset{\mathrm{Nitrogen}\mathrm{dioxide}}{4{\mathrm{NO}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}$