Clojure is a dynamic programming language that targets the Java Virtual
Machine. It is designed to be a general-purpose language, combining the
approachability and interactive development of a scripting language with
an efficient and robust infrastructure for multithreaded programming.
Clojure is a compiled language - it compiles directly to JVM bytecode,
yet remains completely dynamic. Every feature supported by Clojure is
supported at runtime. Clojure provides easy access to the Java frameworks,
with optional type hints and type inference, to ensure that calls to Java
can avoid reflection.

Clojure is a dialect of Lisp, and shares with Lisp the code-as-data
philosophy and a powerful macro system. Clojure is predominantly a
functional programming language, and features a rich set of immutable,
persistent data structures. When mutable state is needed, Clojure offers a
software transactional memory system that ensures clean, correct,
multithreaded designs.

WWW: http://clojure.sourceforge.net/