It is necessary to understand these expressions if one is going to live in Costa Rica. These terms cannot be found in a normal Spanish dictionary.

mala pata – Bad luck. For example: Fue mala pata que él perdiera el trabajo. It was because of bad luck that he lost his job. Mala suerte is the correct way to say bad luck. ¡Salado! can also mean bad luck.
maldoso – an evil minded person or someone with bad intentions. For example: José es un maldoso. Joe is a bad guy.
Mamar- is a verb that means to suck. In Costa Rica it can mean to not take advantage of an opportunity or flunk an exam. For example: María mamó el examen de mate. María failed the math test. Note that the ticos use “mate” instead of matemáticas just like we say math instead of mathematics.
mamaditas – are stupid acts in Costa Rica. Estupideces, babosadas or tonterías are all synonyms in Spanish.
marimacha – a lesbian
mandarina – means tangerine. In Costa Rica it is an old dilapidated car or jalopy. Gajo means the same thing in Costa Rica. El gajo is actually the segment of an orange or tangerine, thus mandarina and gajo are used interchangeably to mean an old car in Costa Rica.
medio 35- a crazy person
mejenga – an informal football game
menear –to move one’s rear end when they dance
menudo – loose pocket change
meter la pata – to put your foot in your mouth
miado – to have bad luck
mico – a vagina
miche – a fight. Pleito is a synonym. Bronca or bochinche are also used here.