Anne is very outgoing, but her sister's quite shy.

outgoing 是由动词短语 go out（外出）加上后缀 -ing 构成的形容词。go out 本意是"出去、外出"，引申为"与人交往"的意思。加上 -ing 后缀后，outgoing 形容一个人"喜欢社交、性格开朗、外向的"。