1. to give a false or misleading appearance to; conceal the truth or real nature of.
2. to put on the appearance of; feign.
3. Obsolete: to let pass unnoticed; ignore.
4. to conceal one’s true motives, thoughts, etc., by some pretense; speak or act hypocritically.
Etymology: alteration (by association with obsolete semble, “to resemble”) of Middle English dissimulen < Latin dissimulāre, from dis-, a Latin prefix meaning “apart,” “asunder,” “away,” “utterly,” or having a privative, negative, or reversing force + simulāre, “to copy”, from similis, “like”.