Entrainment is the process where surrounding environmental air mixes into a cloud's updraft.
When environmental air enters a cumulus cloud updraft, it typically:
Buoyancy in clouds is driven by the temperature difference between the updraft and the environment. Warmer air is more buoyant.
Therefore, entrainment leads to a reduction in the cloud updraft's buoyancy.
What is the shape of a 5 mm rain drop as it falls through the Earth’s atmosphere?