4 Answers

(str?g'?l)

v., -gled, -gling, -gles. v.intr.To exert muscular energy, as against a material force or mass: struggled with the heavy load.To be strenuously engaged with a problem, task, or undertaking: struggled with his math homework.To make a strenuous effort; strive: struggled to be polite.To contend or compete: "Right and wrong ... will ever continue to struggle" (Abraham Lincoln).To progress with difficulty: struggled through the novel.

v.tr.
To move or place (something) with an effort: struggled the heavy desk into the elevator.

n.The act of struggling.Strenuous effort; striving.Combat; strife: armed struggle.

[Middle English struglen.]

struggler strug'gler n.
strugglingly strug'gling·ly adv.

Read more: http://www.answers.com/topic/struggle#ixzz1oZCD51vA

ADDING TO, AND PROBABLY REPEATING SOME:
HARD TRY,   FIGHT TO WIN,   ATTEMPT,   BATTLE,   BRUSH,   CLASH,   COMBAT,   FIGHT,   WRESTLE,   BRAWL,   BUCK,   BUMP HEADS,   COMPETE,   SKIRMISH,   LABOR,    TOIL,   WORK,   EFFORT,   EXERTION

Many different words  like,   To make great efford. (2)  To strive.   (3) A voilent  efford of the body. (4) strife.

The opposite would be "effortless" not trying,