one's age, according to the traditional Chinese method of reckoning (i.e. the number of Chinese calendar years in which one has lived) – In this system, a person's age at birth is one, and increases by one at the beginning of the first solar term 立春[Li4 chun1] each year, rather than on one's birthday.
contrasted with 實歲|实岁[shi2 sui4]
Definitions (粵典–words.hk)
名詞
東亞傳統歲數嘅計法，一出世就當一歲 age of a person, calculated with the East Asian traditional method of counting newborns as 1 year old
參看
虛齡
Definitions (Wiktionary)
noun
nominal age (reckoned by the traditional method, i.e. considering a person one year old at birth and adding a year each lunar new year)
Definitions (Kaifangcidian)
（沒有對應漢語詞彙）
Examples (Tatoeba—Mandarin-English)
Mandarin
他虚岁三十七岁。
他虛歲三十七歲。
tā xū suì sān shí qī suì 。
According to East Asian reckoning, he's thirty-seven.
Examples (Wiktionary)
Mandarin
小时候一直搞不懂周岁和虚岁。刚才朋友说：“周岁是从妈妈身体里出来的时间，虚岁是从爸爸身体里出来的时间。。”我顿时内牛满面地懂了。。
小時候一直搞不懂週歲和虛歲。剛才朋友説：“週歲是從媽媽身體裏出來的時間，虛歲是從爸爸身體裏出來的時間。。”我頓時內牛滿面地懂了。。
xiǎo shí hòu yī zhí gǎo bù dǒng zhōu suì hé xū suì ． gāng cái péng you shuō ： “ zhōu suì shì cóng mā ma shēn tǐ lǐ chū lái de shí jiān ， xū suì shì cóng bà ba shēn tǐ lǐ chū lái de shí jiān ． ． ” wǒ dùn shí nèi niú mǎn miàn de dǒng le ． ．
I have been confused by western age and nominal age [in East Asian culture, where newborns start at the age of one year] since I was young. Just then a friend said: “Western age is when you exit mom's body, and nominal age is when you exit dad's body.” With tears streaming down my face, I suddenly understood everything.