Green’s Dictionary of Slang

mark v.

[mark n.1 ]

1. [mid–late 19C] (UK Und.) to subject to surveillance, e.g. of criminals by the police.

2. [1910s+] (US Und.) to select a prospective victim.

3. [1950s–70s] (US black) to tease, to mock.

In phrases

mark someone’s card (v.) [racecourse use, tipsters mark race-cards with their selections]

1. [1930s+] to watch someone, to place someone under surveillance, to pick someone out as a potential victim.

2. [1940s+] to explain, to point out, to warn.

3. [1960s+] to categorize, usu. either as a good or trustworthy or bad or untrustworthy person; to put someone in a specific position.

4. [1960s+] to realize, to see and understand.

mark up (v.)

1. [1910s+] to bruise, to leave with scars after a fight.

2. [1980s+] (Aus. prison) to tattoo.