acro- Look up acro- at Dictionary.com
word-forming element meaning "highest, topmost, at the extremities," before vowels acr-, from Latinized form of Greek akro- "pertaining to an end, extreme," from akros "at the end, at the top, outermost; consummate, excellent" from PIE *akri-, from root *ak- "be sharp, rise (out) to a point, pierce."