A preposition meaning "against" — identical to the English prefix contra-
Encoding Strategies:
linguistic

counter
against
Contra means against and is the Spanish equivalent of the English word counter0, as in counterattack0 or counter-argument0.
contra
against (opposition),
against, into (direction)
Used when two things are in opposition, or when something moves toward and into something else.
- Estamos en guerra contra el enemigo = We are at war against the enemy
- El coche chocó contra la pared = The car crashed into the wall
against (position)
When something is physically resting or leaning against something else.
- Apoyó la bicicleta contra el muro = She leaned the bicycle against the wall
en contra
against, in opposition
En places you in a state, and contra is that state — a general sense of opposition.
- Voté en contra de la propuesta = I voted against the proposal
- ¿Estás a favor o en contra? = Are you for or against?
a la contra
in opposition, against the grain (attitude),
on the counter, on the counterattack (sports)
A points toward something specific, and la contra is that thing — the counter-position or counter-strategy. So "a la contra" means you're oriented toward that defined stance.
- Siempre va a la contra de todo = He always goes against everything
- El equipo jugó a la contra y marcó dos goles = The team played on the counter and scored two goals