We found one dictionary that defines the word go into one's shell:

General (1 matching dictionary)

1. go into one's shell: Wiktionary

Definitions from Wiktionary (go into one's shell) ▸ verb:  (idiomatic) To act defensively. ▸ Words similar to go into one's shell ▸ Usage examples for go into one's shell ▸ Idioms related to go into one's shell ▸ Wikipedia articles (New!) ▸ Words that often appear near go into one's shell ▸ Rhymes of go into one's shell ▸ Invented words related to go into one's shell