To shoot up is to grow very fast, or to rise sharply. Prices shoot up.
It is used of children between about eleven and fourteen more than of anything else. Costs shoot up faster than they ever come down again.
1phraseshoot upTo grow very fast, or to rise sharply.
“He seemed to shoot up six inches in a single summer.”
shoot up is a phrase.
Practised in A Song of Ice and Fire