an ad hoc organization or process is not planned but is formed or arranged when it is necessary for a particular purpose.

An ad hoc group of 75 parents is leading the protest to demand the resignation of the headteacher.

He doesn't charge a set amount for his work but negotiates fees on an ad hoc basis.

• pull/tear your hair out
• Pull the other leg !
• Pull the other leg it's got bells on!
• Pull the other one !
• Pull the other one it's got bells on!
• pull the plug
• pull the plug on
• pull the plug on something
• pull the rug from under
• pull the rug from under someone
• pull the rug from under something
• pull the rug out from under
• pull the rug out from under someone
• pull the rug out from under something
• pull the strings
• pull the wool over eyes
• pull the wool over someone's eyes
• pull through
• pull through something
• pull together
• pull to pieces
• pull up
• pull up a chair
• pull up by bootstraps
• pull up by your bootstraps