The New Penguin Thesaurus in A-Z Form by Rosalind Fergusson
This comprehensive and easy-to-use thesaurus contains over 400,000 synonyms, listed with antonyms where appropriate and covers standard and colloquial English and slang. It lists words closest in meaning first, and includes helpful examples to illustrate the nuances of particular words. Hundreds of newly coined words and expressions are included, from "e-tailing" and "guesstimate" to "chill out" and "snail mail".