Subtle in Chinese / Japanese...

拈華微笑 is a Chinese, Korean, and Japanese Buddhist title that relays the idea of “heart-to-heart communication,” or “thought transference.”

The literal translation is, “holding a flower and subtly smiling,” or “the holding of a flower with a subtle smile.” It is the visual act and emotion that communicates more volume than words can say.

幽玄 is the Chinese, Japanese Kanji, and old Korean Hanja word meaning dim, deep, mysterious, subtle grace, hidden beauty, mysterious profundity, elegant simplicity, or subtle and profound.

This can also be the Japanese personal name Yuugen or Yugen.

In Chinese and Korean, 博愛 means a universal fraternity, brotherhood, or universal love.

In Japanese, this means charity, benevolence, philanthropy, or love for humanity.

Please note these subtle differences and take that into account depending on your intended audience (Chinese, Korean or Japanese).

See Also:  Benevolence | Altruism

鏡花水月 is an old Asian proverb that means “flowers in a mirror and the moon reflected in the lake” or “flowers reflected on a mirror and the moon reflected on the water's surface.”

Literally, 鏡花水月 reads “Mirror Flower, Water Moon.”

Figuratively this can be used to represent a lot of different ideas. It can be used to express an unrealistic rosy view or viewing things through rose-tinted spectacles. So you can use it to relay an idea about something that is visible but has no substance, something that can be seen but not touched, or something beautiful but unattainable such as dreams or a mirage.

This expression is used to describe things like the subtle and profound beauty of poems that cannot be described in words.

鏡 = Mirror (or lens)
花 = Flower(s)
水 = Water
月 = Moon

Can also be written 水月鏡花 (just a slight change in word/character order).

虚実 is a Japanese word that means “falsehood [and] truth” or “fiction [and] fact.”

This concept is used in warfare, gameplay, and martial arts strategies. 虚実 can be a strategy of real and/or deceptive moves. This gets to some Sun Tzu Art of War stuff where in warfare a strategic move is either a real and serious move or it is a deceptive blow.

Let's explore each character in more depth:

虚 was originally written 虛 (there is a very subtle difference in the strokes at the bottom of the character) and means unpreparedness, falsehood, emptiness, void, abstract theory, empty or unoccupied, diffident or timid, false, humble or modest, virtual, or in vain.
In the Buddhist context, 虛 represents the Pali/Sanskrit word “śūnya,” meaning empty, vacant, unreal, unsubstantial, untrue, space, humble, or in vain.
In ancient Eastern/Chinese astronomy, 虛 represents the “Emptiness” constellation (one of the 28 mansions in the sky).

実 was originally 實 in Chinese (they currently write it as 实 in Simplified Chinese) with the meaning, truth, reality, sincerity, honesty, fidelity, and substance.
The Buddhist context is similar, adding real, true, honest, really, solid, definitely, sincere, solid, fixed, full, to fill, fruit, kernel, verily, in fact, the supreme fact, or ultimate reality to the definition.