adverb
Adverbial intensifier, similar to とても or 非常に but often somewhat formal, literary, or old-fashioned in everyday speech.
祖母はその知らせを聞いて、たいそう喜んだ。
My grandmother was very pleased to hear the news.
na-adjective
considerable; excessive; large in amount or number
Na-adjective use for a quantity, amount, degree, or scale that is large, considerable, or sometimes more than expected.
それはたいそうな金額ですね。
That is a considerable amount of money.
na-adjective
splendid; impressive; tremendous
Positive or admiring na-adjective use for something grand, impressive, or splendid in scale or appearance.
たいそうなごちそうを用意してくれた。
They prepared a splendid feast for us.
na-adjective
exaggerated; overblown; grandiose
Used when something is made to sound grander, more serious, or more important than it really is; common in phrases such as たいそうなこと.
そんなたいそうな話ではありません。
It is not such a big, exaggerated matter.