Apache Mahout(TM) is an open source project that is primarily used for creating scalable machine learning algorithms. It implements machine learning techniques such as, collaborative filtering, clustering, recommendation and classification.
It also provides Java libraries for common math operations (focused on linear algebra and statistics) and primitive Java collections.
A mahout is a word used in South Asian countries to describe one who drives an elephant as its master. The name comes from its close association with Apache Hadoop which uses an elephant as its logo. Many of the implementations use the Apache Hadoop platform.