1A dog -- a domesticated mammal commonly kept as a pet, known for barking, guarding the house, and being taken for walks.
毎朝、犬を散歩に連れて行く。
I take the dog for a walk every morning.
近所に新しい犬が引っ越してきたらしい。
It seems a new dog moved in nearby.
子どもたちは公園で犬と遊んでいた。
The children were playing with a dog in the park.
うちの犬は知らない人を見ると吠える。
Our dog barks whenever it sees a stranger.
2A derogatory slang term for an informer, snitch, or spy -- often written in hiragana (いぬ) and used as an insult toward a traitor.
裏切り者はみんなから「いぬ」と呼ばれた。
The traitor was called a snitch by everyone.
警察に情報を流したことがバレて、彼は仲間から犬呼ばわりされた。
When it came out that he had leaked information to the police, his colleagues branded him a snitch.
3A vulgar insult for a contemptible or worthless person; also used for someone who servilely does another's bidding, i.e. a lapdog.
あいつは会社の犬になって、上司の言いなりだ。
That guy has become the company's lapdog, doing whatever his boss says.
彼は約束を破ったので、仲間から犬呼ばわりされた。
He broke his promise, so his friends called him a worthless dog.
4An old prefix attached to certain words to add the meaning inferior, futile, or counterfeit. In modern Japanese it survives only in a few fixed words such as 犬死に (a pointless, wasted death).
昔の言葉では「犬死に」のように、「犬」が「無駄な」という意味を加えることがある。
In old usage, 犬 could form words like 犬死に, adding a sense of futile or wasted.