1. To judge, inspect, compare, or ascertain the veracity of something or someone and the inability to proceed until the situation is resolved.
2. To be in the object of act described in Def 1, typically with a negative connotation.
(Possible origins: to "grill
" someone/something; Or relating to the nautical term "in irons" (viz "points of sail") i.e., unable to move)
"We have two wedding caterers on the irons at the moment, so we will see who is the better one to go with."
"Jeffrey in accounts is on the irons until they find out if he erred or if it was Bob in IT that made the mistake."