IPA: /ˌɪntrəˈmʌskjʊlər/
KK: /ɪntrəˈmʌskjələr/
Relating to something that is located inside a muscle or is administered directly into a muscle.
The doctor gave her an intramuscular injection to help with the pain.
Intramuscular → It is formed from "in-" (meaning within) and "musculus" (meaning muscle). The word describes something that is located or occurring within the muscle.
Think of something happening 'within' ('in-') the 'muscle' ('musculus') — that's why intramuscular refers to something inside the muscle.