Master Yourself in Chinese / Japanese...

提防律師 is a kind of Chinese joke about lawyers.

The first two characters mean “guard yourself against (an attack)” or “beware.”
The last two characters can be translated as lawyer, attorney, or solicitor.

Separately, those characters mean law/regulation/control and master/expert/teacher. Here, you can see the attorney meaning is pretty clear in the individual characters.

Please note this is Chinese only (it won't make sense in Japanese, and the last two characters are sometimes translated together as “Buddhist Priest” in Japanese).

The 浪人 or Ronin have no master - The most famous are the 47 ronin created after their Lord committed suicide. This term was not a positive title for the Samurai of ancient Japan. However, in recent years, movies and video games have glorified the term Ronin.

In Chinese, this term has the original meaning of a hobo, vagabond, or ruffian.
In Korean Hanja, these characters would be read as adventurer, wanderer, someone without a steady job, or someone who is wasting away time.

In modern Japan, this term is used as a nickname for a high school student who has failed a college entry exam (and is trying again).

In Chinese and Korean, the Japanese definition of “Masterless Samurai” is known because of the historical context. Even in Japanese, the literal translation is closer to the Chinese and Korean definitions shown above.

This will make a fine wall scroll if you are a fan of the Ronin or see yourself as a Ronin of sorts. However, please think twice before getting a Ronin tattoo!

空無 is “nothingness” in a Buddhist context.

The first character means empty but can also mean air or sky (air and sky have no form).

The second character means have not, no, none, not, or to lack.

Together these characters reinforce each other into a word that means “absolute nothingness.”

I know this is a term used in Buddhism, but I have not yet figured out the context in which it is used. I suppose it can be the fact that Buddhists believe that the world is a non-real illusion, or perhaps it's about visualizing yourself as “nothing” and therefore leaving behind your desire and worldliness.
Buddhist concepts and titles often have this element of ambiguity or, rather, “mystery.” Therefore, such ideas can have different meanings to different people, and that's okay. If you don't get it right in this lifetime, there will be plenty more lifetimes to master it (whatever “it” is, and if “it” really exists at all).

Soothill defines this as “Unreality, or immateriality, of things, which is defined as nothing existing of independent or self-contained nature.”

盡忠報國 is a proverb that is the tattoo worn on the back of Yue Fei, a famous Chinese warrior who lived until 1142 A.D.

The tattoo can be translated as “Serve the country with the utmost loyalty.” More literally, it means “[The] Ultimate Loyalty [is too] Duty [of] Country.”

Legend has it that this tattoo once saved his life when he was accused of treason.

The first two characters have come to create a word that means “serve the country faithfully” or “die for the country.” Note: It's more a willingness to die for one's country than the actual act of dying.

The last two characters have come to mean “Dedicate oneself to the service of one's country.”

Both of these words are probably only in the Chinese lexicon because of this famous tattoo.

If you break it down, character-by-character, here is what you get:
1. To the utmost, to the limit of something, the ultimate.
2. Loyalty or duty (a sense of duty to one's master, lord, country, or job).
3. Report, recompense, give back to (in this case, you are giving yourself to your country as payback).
4. Country, state, nation, kingdom.

More about the famous warrior and army general, Yue Fei