Merriam-Webster Collegiate Dictionary - er

 abbreviation  1. earned run  2. emergency room ER  symbol erbium ER  I. adjective suffix or adverb suffix  Etymology: Middle English ~, ~e, -re, from Old English -ra (in adjectives), -or (in adverbs); akin to Old High German -iro, adjective comparative suffix, Latin -ior, Greek -ion — used to form the comparative degree of adjectives and adverbs of one syllable hotter drier and of some adjectives and adverbs of two or more syllables completer beautifuller  II. noun suffix  also -ier or -yer  Etymology: Middle English ~, ~e, -ier, -iere; partly from Old English ~e (from Latin -arius); partly from Old French -ier, -iere, from Latin -arius, -aria, -arium -ary; partly from Anglo-French ~e, from Latin -ator -or — more at -ary, -or  1.  a. person occupationally connected with furrier lawyer  b. person or thing belonging to or associated with header old-timer  c. native of ; resident of cottager New Yorker  d. one that has three-decker  e. one that produces or yields porker  2.  a. one that does or performs (a specified action) batter — sometimes added to both elements of a compound builder-upper  b. one that is a suitable object of (a specified action) broiler  3. one that is foreigner — in all senses -yer in a few words after w, -ier in a few other words, otherwise ~ ER  int~jection  Date: 1862 — used to express hesitation