Place apple slices in a 3-1/2- or 4-quart slow cooker. Stir in sugar, water, vinegar, cinnamon, cloves, allspice and nutmeg.
Cover; cook on high-heat setting for 5 to 6 hours. Stir. Cool mixture at least 1 hour or cover and chill overnight.
Ladle apple butter into half-pint storage or freezer containers, leaving a 1/2-inch head space. Seal and label. Store 3 weeks in refrigerator or for 1 year in freezer. Makes 4 half-pints.