Phthisicky is a rarely used term and is spelled with a silent "p" followed by "th". The correct pronunciation, according to IPA phonetic transcription, is /θɪzɪki/. The "th" sound is pronounced as in the word "thin" and the "s" is pronounced as "z". The "-ick" ending indicates an adjective form. Phthisicky is related to phthisis, an archaic term for tuberculosis of the lungs. It describes anything related to or resembling the disease, such as a pale and wasted appearance.
1. Phthisical. 2. Asthmatic.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.