# What is spontaneous in spontaneous symmetry breaking

When we say spontaneous symmetry breaking what do we mean by "spontaneous"?

The dictionary, for a non native speaker, relates it to the absence of an external stimulus.

In QFT and SM it simply says that Lagrangian remains symmetric but the quantum vacuum state breaks such an invariance.

Are we considering the field operator as something external?

Are we considering an explicit breaking something external?