Dreamed vs. Dreamt
Dreamed and dreamt are both allowable past tense forms of the verb dream. Dreamt is often described as the British version of the word (1, 2, 3), however, a Google Books Ngram search shows that dreamed is more common than dreamt in both British and American English. Still, dreamt is on more equal footing in Britain than in America.

Key Differences
"Dreamt" is the past tense and participle of "to dream". "Dreamed" isn't a word. It's like when some people say "taked" nowadays for the past tense of "to take".
Dreamt is especially common in British English; while American writers use dreamt about a tenth as often as dreamed, British writers use dreamt about a third of the time.
Dreamt means Experience while sleeping (past tense of 'dream'), dreamed means conceived of or imagined or hoped for.
Dreamed is preferred in all main varieties of English as compared to dreamt.
Writers choose dreamt or dreamed depending upon their style of writing.

Janet White
Nov 27, 2015
If you are excited about a dream you saw and discussing it with a friend, you would of course say that you dreamed about winning a lottery.
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Following grammar, Dreamed and dreamt are two forms of the past tense of dream, and there is no difference between the two.
Dreamt is more often used in the figurative senses of the word, especially in the phrase dreamt up, while dreamed is more likely to denote the mental activity that occurs during sleep. But this is by no means a rule, and both words are used both ways.

Aimie Carlson
Nov 27, 2015
People believe that dreamt is a better option than dreamed that looks dull for a wonderful mental activity such as a dream.

Samantha Walker
Nov 27, 2015
Dreamed and Dreamt Definitions
Dreamed
A series of images, ideas, emotions, and sensations occurring involuntarily in the mind during certain stages of sleep.
Dreamt
A past tense and a past participle of dream.
Dreamed
A daydream; a reverie.
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Dreamt
Simple past tense and past participle of dream
Dreamed
A state of abstraction; a trance
Wandering around in a dream.
Dreamt
Or only extant in a dream or dreams.
Dreamed
A condition or achievement that is longed for; an aspiration
A dream of owning their own business.
Dreamed
A wild fancy or unrealistic hope
He knew that playing for a professional team was only a dream.
Dreamed
(Informal) One that is exceptionally gratifying, excellent, or beautiful
Her boyfriend is a dream.
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Dreamed
To experience a dream in sleep
Dreamed of meeting an old friend.
Dreamed
To daydream
Sat there dreaming during class.
Dreamed
To have a deep aspiration or hope
Dreaming of a world at peace.
Dreamed
To regard something as feasible or practical
I wouldn't dream of skiing on icy slopes.
Dreamed
To experience a dream of while asleep
Did it storm last night, or did I dream it?.
Dreamed
To conceive as possible; imagine
We never dreamed it would snow so much.
Dreamed
To have as an aspiration or hope
She dreams that she will become a pilot.
Dreamed
To pass (time) idly or in reverie.
Dreamed
Simple past tense and past participle of dream
Dreamed
Conceived of or imagined or hoped for;
His dreamed symphony that would take the world of music by storm
What is Dreamed?
Dreamed means experiencing dreams during sleep or urging to imagine something. If you are excited about a dream you saw and discussing it with a friend, you would of course say that you dreamed about winning a lottery
What is Dreamt?
Dreamt is a simple past tense and past participle of dream. Dreamt is common in British English. Dreamt is more often used in the figurative senses of the word, especially in the phrase dreamt up.