Definitions:

1. Describes mannerisms or behaviors associated with femininity when displayed by a boy or man. ADJECTIVE
   • The character was criticized for being portrayed in a sissyish way.
2. Suggests being overly cautious, fearful, or lacking in assertiveness. ADJECTIVE
   • He was teased for his sissyish reluctance to join the rough sports game.

Synonyms:

• delicate
• effeminate
• emasculate
• timid
• unmanly
• weak