Merriam-Webster's Collegiate® Dictionary, 11th Edition
FOLD
I. noun
Etymology: Middle English, from Old English falod; akin to Old Saxon faled enclosure Date: before 12th century an enclosure for sheep,
2. a flock of sheep, a group of people or institutions that share a common faith, belief, activity, or enthusiasm,
II. transitive verb Date: before 12th century to pen up or confine (as sheep) in a fold,
III. verb
Etymology: Middle English, from Old English fealdan; akin to Old High German faldan to fold, Greek diplasios twofold Date: before 12th century transitive verb to lay one part over another part of , to reduce the length or bulk of by doubling over , to clasp together ; entwine , to clasp or enwrap closely ; embrace , to bend (as a layer of rock) into folds,
6. to incorporate (a food ingredient) into a mixture by repeated gentle overturnings without stirring or beating, to incorporate closely,
7. to concede defeat by withdrawing (one's cards) from play (as in poker), to bring to an end, intransitive verb to become doubled or pleated, to fail completely ; collapse , to fold one's cards (as in poker), foldable adjective
IV. noun
Date: 13th century
a part doubled or laid over another part ; pleat , something that is folded together or that enfolds,
3. a bend or flexure produced in rock by forces operative after the depositing or consolidation of the rock, an undulation in the landscape, a margin apparently formed by the doubling upon itself of a flat anatomical structure (as a membrane), a crease made by folding something (as a newspaper)