in one's shell

in one's shell or into one's shell  {adv.} or  {adj. phr.},  {informal}
In or into bashfulness; into silence; not sociable; unfriendly.
After Mary's mother scolded her, she went into her shell.
The teacher tried to get Rose to talk to her, but she stayed in her shell.
Categories: {adj. phr.} {adv.} {informal}