Subservient
Abject
noun, な adjective
A lowly person who yields to everyone is really subservient. They'll do everything people tell them because they don't have the nerves to speak up and just say no.
ひくつ
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
どうしてすぐに卑屈になるの？
Why do you immediately become subservient?