1. grow or increase very quickly
sales of the product have shot up recently
The phrasal verb 'shoot up' has a number of meanings. If something or someone 'shoots up' it means to grow or increase considerably in a short space of time, this use is usually related to growth. To 'shoot up' is also an informal way of describing someone injecting a narcotic drug. 'Shoot up' can also mean to cause damage to a person or place with a gun.