Meaning of 負犬 in Japanese

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Definition of 負犬

いぬ(inu) 【犬 ·狗】

(n) dog (Canis (lupus) familiaris)
彼女は吠える犬を怖がる。
She is afraid of barking dogs.
snoop (i.e. a detective, a spy, etc.)
気をつけて。警察の犬がかぎ回ってる。
Watch out! A police spy is snooping around.
(n-pref) counterfeit; inferior; useless; wasteful

ふ(fu) 【負】

おい(oi) 【笈 ·負】

(n) wooden box carried on one's back to store items for a pilgrimage
あ、あれ？なんか・・・すっごい負のオーラを感じますよ？
E-eh? I somehow seem to feel a very threatening aura...