Definitions
1.verbTo make thin or thinner.
2.verbTo become thin or thinner."The crowds thinned after the procession had passed: there was nothing more to see."
3.verbTo dilute.
4.verbTo remove some plants or parts of plants in order to improve the growth of what remains.
5.nounProcess of removing plants or parts of plants to facilitate the growth of other plants
6.nounWood, leaves, or other plant parts removed during the process of thinning
7.nounThe action or result of reducing thickness, density, or number
8.adjectiveBecoming less thick, dense, or numerous"thinning hair"