What is the meaning of equilibrium in mechanics and equilibrium in thermodynamics?

Explanation

Equilibrium in mechanics means that net external force and torque on a system are zero. Equilibrium in thermodynamics means if the macroscopic variable that characterise the system do not change in time then thermodynamics system is in equilibrium.
Whether or not a system is in a state of equilibrium depends on the surroundings and the nature of the wall that separates the system from the surroundings.
For example, a gas inside a closed rigid container completely isulated from its surrounding with fixed value of pressure, volume, temperature, mass and composition that do not change with time is in a state of thermodynamic equilibrium.