Glossaries for Space Adventurers and Mere Mortals
On-line glossaries are now available for a wide variety of subjects.
Here are some examples...

Glossary of Space Terms from A-Z
If you ever wonder the meaning of an astronomical word, check out this site to find the definition of the space term, from Absolute Magnitude to Zodiacal Light (no, it's not what you think).

Glossary of Education Reform
Created by the Great Schools Partnership, the Glossary of Education Reform is a comprehensive online resource that describes widely used school-improvement terms, concepts, and strategies for journalists, parents, and community members.

Glossary of Shakespeare's Words
Understanding 16th century English can be a challenge for students. This site lists thousands of words, from abjure to wot, provides their definition, and shows where each word can be found within the works of William Shakespeare.

Computer Terms Glossary
Computer hope has compiled 12,000 computer and technical terms and definitions, broken out by areas like Cell Phones and Gaming. Learn the different between WiFi and Widget or Bits, Bytes and Bricked.

Fremont Union High School District: Glossary of Terms
School districts and individual schools are creating their own glossaries of terms for parents, staff and students. This example was from the Fremont Union High School District in California.

Urban Dictionary
Urban Dictionary is a crowd sourced, online dictionary of slang words and phrases. While not appropriate for younger students, this site has become a go-to resources for parents and teachers trying to understand or decode their child's communications.
Warning! This is one of the few web sites that identifies and defines pretty much every term currently in use, including the very inappropriate ones.

Library of Babel
This is one of those sites that hard to describe, but interesting in many ways. The site combines the notion of an infinite number of monkeys at an infinite number of typewriters combined with a search engine.
As the site says, it's is a place for scholars to do research, for artists and writers to seek inspiration, for anyone with curiosity or a sense of humor to reflect on the weirdness of existence.
One practical use for this site is word inspiration. Search for a few words or a sentence, and select the with random English words result. What you entered will be surrounded with random words, some nonsense, many interesting.
You can also use it to create a word search for your students. See if they can find the special message.
Glossaries are available for almost any subject.
Using Google or your favorite search engine, type in the subject's name followed by the word glossary to find specific on-line resources.
Other Areas To Check Out ...
● Black History
● Thoughts on Educational Reform
● On-Line Collections and Research Guides
● School Reform Models (K-12)
● Images of Space
● Linking The Real World and Physics