The term "stiff" has several meanings, depending on its context.
1) In a physical sense, it can refer to something that is rigid or inflexible in nature - for example, a stiff breeze means there's a strong wind blowing.
2) It can also be used figuratively to describe someone who is very proper and formal in their behavior, often seen as aloof or unfriendly - such as a person with a "stiff upper lip."
3) In the context of finance, it means an asset that has decreased in value. For example, if you invest money into stocks and they decrease in price, your portfolio may be described as being stiff due to the losses.