Otus Lisp (Ol in short) is a purely functional dialect of Lisp.
It implements an extended subset of the R7RS Scheme, including but not limited to some SRFIs. It is tiny (~ 64KB), embeddable and cross-platform. Provides a portable, high-level interface to call code written in another language.
You can use Ol in Linux, Windows, macOS, Android, BSD (and its descendants), webOS, Solaris and other operating systems based on various hardware architectures (intel, arm, ppc, mips, etc).
Also, Ol is ported to the Web (in WebAssembly form) and can be used in Chrome, Firefox, Opera, Iceweasel, Epiphany, SeaMonkey, Luakit, Iceape, etc.
A project page with an interactive Ol session is available.