The crossword solution for the term WORD WITH ACID OR FIELD is TEST, which is a four-letter word. TEST is a noun that can refer to an examination or assessment of a person's knowledge, skills, aptitude, physical fitness, or classification in many other topics. It can also refer to a procedure intended to establish the quality, performance, or reliability of something, often prior to public release. Tests are also used to measure the presence or concentration of a substance, such as an acid or a field.