piorthopnea 1. Dyspnea while lying down, due to obesity. 2. Difficulty breathing in any but the erect posture, due to obesity. Related fat-word units: adipo-; lard; lipo-; obeso-; oleo-; omento-; pimelo-; sebo-; steato-. Found on http://www.wordinfo.info/words/index/info/view_unit/1678/