Master is the one who has the thorough control over his mind, body and senses. He / She is the master of meditation.
Guru is a realised Soul. But due to lack of vocabulary, Guru is often called as a master, like in the Gospel of Sri Ramakrishna (English Translation), Sri Ramakrishna is often called as Master.
Swami is a term used to address a monk. He may or may not be realised. A swami may be a master, a teacher or an advanced student. Initial, fresh renunciates are called as brahmacharis.
An Acharya is a teacher who spreads spirituality wherever he / she goes.