牛津高階詞典的解釋:
phew
/ fju:; fju/ (also whew) interj (written representation of a short soft whistling sound made by blowing out or sucking in one's breath, and used to express relief, exhaustion or amazement 呼氣或吸氣發出的很短的口哨聲, 用以表示松口氣、 疲勞或驚奇): Phew! That was a nasty moment -- that car nearly hit us. （發出口哨聲）當時可真危險--那輛汽車差點撞上我們.
2 要用壹句話表達的話, 老外也有類似的表達方法, 那就是: Now I can breathe freely (again). (不妨google壹下)
除了breathe freely以外也可用breathe easily 或breathe easy或rest easy
美國傳統詞典給出的解釋如下:
To be relaxed or relieved, especially after a period of tension.
松壹口氣，放下心來：尤指壹段時間的緊張後放松或解脫
來看更多詞典的補充用法和例句:
breathe (easily/freely) again
=to relax because you are no longer in a difficult or dangerous situation:
We found that file, so you can breathe again.
Just three more questions and then you can breathe easy.
rest/breathe easy:
=to stop worrying
--We can rest easy now - we've got everything under control.
somebody can breathe easy/easily:
used when saying that someone can relax because a worrying or dangerous situation has ended.
--With stocks going up, investors can breathe easily.
5 (idm 習語) (be able to) breathe (easily/freely) again
= feel calm or relieved after a period of tension, fear or exertion; relax （在壹度緊張、恐懼或努力之後）恢復平靜或安下心來; 松口氣:
Now my debts are paid I can breathe again. 現在我已還清欠債, 可以松口氣了.