Though tax complexity is a frequent topic of debate, the difficulty of defining or measuring what is meant by complexity is a stumbling block to tax simplification. Most measures of tax complexity are indirect or anecdotal. One dimension of tax complexity is addressed by the courts at an operational level—the final decision on the meaning of key words in a tax controversy. Faced with a word whose meaning is unfamiliar, unclear, or ambiguous, but critical to a tax dispute, the result may be a fork in the road. Is the term defined by statute, is it a term of art, or is it an ordinary English word? After exploring the courts' stated reliance on dictionaries in appropriate circumstances, the paper presents over 200 examples drawn from tax case law. Based on the courts' apparently increasing role as final arbiter of meaning in tax disputes, we suggest a general approach for slowing the pace of tax complexity.