adj.
Pronunciation: in- ˌ ves-t ə - ' g ā -shn ə l, -sh ə -n ə l
Function: adjective
Date: 1905
1 : of or relating to investigation < investigational activities>
2 : relating to or being a drug or medical procedure that is not approved for general use but is under investigation in clinical trials regarding its safety and efficacy <an investigational new drug>