Print: REF PE 1625 .O87 1989 (20 vols) and REF PE 1625 .O92 1993 (3 vols)
The "OED," originally called New English Dictionary on Historical Principles [REF PE 1625 .N53 1888, 10 vols], is the definitive guide to the meaning, history, and pronunciation of over half a million words, tracing the usage of words from across the English-speaking world through quotations from international English language sources. Its intention was to record every word used in English since 1150 and trace it back through all its shifting meanings, spellings and uses to its earliest recorded appearance, plus at least one citation for each century of its existence. As a historical dictionary, the OED is very different from Dictionaries of current English, in which the focus is on present-day meanings. You’ll find present-day meanings in the OED, but also the history of individual words, and of the language.
The online version can be searched in a variety of ways: by word; phrase; definition; etymology; by author of the quotations which shows how the use of a word has changed over time. It is not exhaustive in its coverage of standard vocabulary and is limited in its treatment of slang, dialect, scientific, and technical terms, so other dictionaries should be used as well.

DSL brings together the two major historical dictionaries of the Scots language:
A Dictionary of the Older Scottish Tongue (DOST) Older Scots - 12th century - 1700 and The Scottish National Dictionary (SND)
Modern Scots - 1700 - 2005.

Howe Library Reference (1st Floor) ; PE2843 .D52 1985
Focuses on the regional aspects of American English, documenting words, phrases, and pronunciations that vary from one place to another. This online version provides interactive maps, audio field recordings, and fielded searching.

This is the "OED" of slang, tracing the usage of slang terms over five centuries in all English-speaking regions of the world. Over 100,00 terms are defined, with each word authenticated by genuine and full-referenced citations of its use. Emphasis is on etymology.

Drawing on the OED, covers over 6,000 slang words and expressions of the English-speaking regions of the world from the 20th and 21st centuries. Provides illustrative quotations and full details of origins and dates of first printed use.

Idiom: a group of words established by usage as having a meaning not deducible from those of the individual words (e.g. over the moon, see the light).
Contains entries for over 6,000 idioms.

Allusions: forms an extension to the English language, drawing on our collective knowledge of literature, mythology, and the Bible to give us a literary shorthand for describing people, places, and events, e.g. thought police, thirty pieces of silver, etc.