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a. (of a nuclear weapon) producing little or no radioactive fallout or contamination
b. uncontaminated
2. (of a wound, etc.) having no pus or other sign of infection
3. Aeronautics causing little turbulence; streamlined
4. (of an aircraft) having no projections, such as rockets, flaps, etc., into the airstream
5. Nautical of a vessel
a. having its bottom clean
b. having a satisfactory bill of health
6. Old Testament
a. (of persons) free from ceremonial defilement
b. (of animals, birds, and fish) lawful to eat
7. New Testament morally and spiritually pure


i. An aircraft that is not carrying external stores like drop tanks or armament.
ii. An aircraft in flight but with the undercarriage, flaps, and airbrakes retracted.


A lazy higher-order purely functional language from the University of Nijmegen. Clean was originally a subset of Lean, designed to be an experimental intermediate language and used to study the graph rewriting model. To help focus on the essential implementation issues it deliberately lacked all syntactic sugar, even infix expressions or complex lists,

As it was used more and more to construct all kinds of applications it was eventually turned into a general purpose functional programming language, first released in May 1995. The new language is strongly typed (Milner/Mycroft type system), provides modules and functional I/O (including a WIMP interface), and supports parallel processing and distributed processing on loosely coupled parallel architectures. Parallel execution was originally based on the PABC abstract machine.

It is one of the fastest implementations of functional languages available, partly aided by programmer annotations to influence evaluation order.

Although the two variants of Clean are rather different, the name Clean can be used to denote either of them. To distinguish, the old version can be referred to as Clean 0.8, and the new as Clean 1.0 or Concurrent Clean.

The current release of Clean (1.0) includes a compiler, producing code for the ABC abstract machine, a code generator, compiling the ABC code into either object-code or assembly language (depending on the platform), I/O libraries, a development environment (not all platforms), and documentation. It is supported (or will soon be supported) under Mac OS, Linux, OS/2, Windows 95, SunOS, and Solaris. E-mail: <>. Mailing list: <>.

["Clean - A Language for Functional Graph Rewriting", T. Brus et al, IR 95, U Nijmegen, Feb 1987].

["Concurrent Clean", M.C. van Eekelen et al, TR 89-18, U Nijmegen, Netherlands, 1989].



1. Used of hardware or software designs, implies "elegance in the small", that is, a design or implementation that may not hold any surprises but does things in a way that is reasonably intuitive and relatively easy to comprehend from the outside. The antonym is "grungy" or crufty.

2. To remove unneeded or undesired files in a effort to reduce clutter: "I'm cleaning up my account." "I cleaned up the garbage and now have 100 Meg free on that partition."
References in classic literature ?
Now some people say that little Lucie had been asleep upon the stile-- but then how could she have found three clean pocket-handkins and a pinny, pinned with a silver safety-pin?
Then, get sponges and clean water to swill down the tables and seats.
We asked him if he had ever tried washing flannels in the river, and he replied: "No, not exactly himself like; but he knew some fellows who had, and it was easy enough;" and Harris and I were weak enough to fancy he knew what he was talking about, and that three respectable young men, without position or influence, and with no experience in washing, could really clean their own shirts and trousers in the river Thames with a bit of soap.
My anxiety about clothing was increased because of the fact that General Armstrong made a personal inspection of the young men in ranks, to see that their clothes were clean.
Yes, Dmitri, clean ones, please," said the countess, sighing deeply.
Plant all the trees in the compound, even if you have to clean out the palms later on.
You are becoming something different, something not so healthy, not so clean, not so nice.
I should not care to see my daughter, my one daughter, who is so clean and pure, love a man like him.
Please to excuse me, miss," she said with a last horrified look at her venerable visitor; "I really can't stand the sight of such a blot of dirt as that in my nice clean parlor.
I tell you I have to live clean to be in condition like this.
to sweet, sense to sentiment, wit to humor and clean English to slang.
Here was Youth, clean and wholesome, unsullied--the thing of glory and wonder for men to conjure with.