Ideas Idioms

a bee in one's bonnet	A person who has a bee in their bonnet has an idea which
	constantly occupies their thoughts.
	"She's got a bee in her bonnet about moving to New York!"
A figment of one's imagination	To refer to something as a figment of one's imagination
	means that an appearance, event or incident is not
	considered to be real but is only imaginary.
	"Other people saw the car, so it's not a figment of Tom's
	imagination!"
A flight of fancy	To refer to an idea or plan as a flight of fancy means that it is
	very imaginative but not at all practical or sensible.
	"He often comes up with good ideas but his latest proposal is just
	a flight of fancy!"
Light bulb moment	A light bulb moment is when you have a sudden moment of
	inspiration, comprehension or realization.
	"Harry had a light-bulb moment when he finally realized what was
	blocking the mechanism."
All in your head	If something is all in your head, it is not real. It is in your imagination.
	"Don't be silly.  Nobody is trying to harm you.  It's all in hour head!"
A mind of your own	If you have a mind of your own, you are capable of forming an
	opinion and making decisions without being influenced by others.
	"That boy doesn't need any advice; he's got a mind of his own."
Never mind	When you say "never mind" to someone, you are telling them not
	to worry, that it is not important.
	"When the child broke the cup Susan said : "never mind - it was
	an old cup."
One-track mind	If you have a one-track mind, you have a tendency to think
	about only one subject.
	"That boy has got a one-track mind; all he thinks about is
	football!"
Take your mind off (something)	If an activity takes your mind off something that you are worrying
	about, it helps you to stop thinking about it for a while.
	"Sarah was worried about the result of the test so Tom took her to
	the cinema to take her mind off it."
Take the words out of	If you say exactly what someone else was going to say,
somebody's mouth	you take the words out of their mouth.
	" I think so too. You took the words out of my mouth."
Think again	If you tell someone to think again, you advise them to
	reconsider the situation and perhaps change their decision.
	"Your apartment is so well located;  you should think again
	before selling it. '
Think outside the box/	People who think outside the box try to find innovative ideas
think out of the box	or solutions.
	"Our competitors are more creative than us - they really think
	outside the  box.
A penny for your  thoughts	This phrase is used to ask someone what they are thinking
	about.
	"You look pensive.  A penny for your thoughts."
Perish the thought	This expression is used when the speaker really hopes that
	something will not happen.
	"If I lost my job, perish the thought, I don't know how we'd
	survive."
Train of thought	A sequence of connected ideas is called a train of thought.
	"I was considering the different options when the noise outside
	broke my train of thought."
Shot in the dark	To refer to a question or statement as a shot in the dark
	means that it is a complete guess, but at the same time it
	might be close to the truth.
	"He didn't know which players had been selected, so mentioning
	Carter's name was just a shot in the dark."
Voice in the wilderness	If you are the only person expressing a warning or an opinion on a matter
	which is ignored by most others, you are a voice in the wilderness.
	"For many years she was a voice in the wilderness protesting against
	child labour."

from http://www.learn-english-today.com/idioms/idiom-categories/thoughts-ideas.htm