R.L. Trask 
A Dictionary of Grammatical Terms in Linguistics [PDF ebook] 

This dictionary of grammatical terms covers both current and traditional terminology in syntax and morphology. It includes descriptive terms, the major theoretical concepts of the most influential grammatical frameworks, and the chief terms from mathematical and computational linguistics. It contains over 1500 entries, providing definitions and examples, pronunciations, the earliest sources of terms and suggestions for further reading, and recommendations about competing and conflicting usages. The book focuses on non-theory-boumd descriptive terms, which are likely to remain current for some years.
Aimed at students and teachers of linguistics, it allows a reader puzzled by a grammatical term to look it up and locate further reading with ease.