A contraction of the word “sabering,” it refers to cutting down or wounding with a saber, a heavy cavalry sword with a curved blade and a single cutting edge.
"Someone had blundered. ..."See in text(Text of the Poem)
“To blunder” means to make a stupid or careless mistake. The line refers to the Light Brigade’s having been ordered into the valley through a careless error in military leadership and communications among the soldiers’ commanding officers.
"Half a league, half a league,
..."See in text(Text of the Poem)
Half a league is about a mile and a half, the distance the British cavalry brigade had to ride through the valley to reach the enemy’s artillery battery. The repetition of “half a league” emphasizes the dactylic meter in the phrase—one stressed syllable followed by two unstressed syllables; the rhythm suggests the rhythm of the horses’ galloping gait.
"Volleyed and thundered; ..."See in text(Text of the Poem)
"Volleyed" means a number of cannons all firing at once. "Thundered" would be the sound of these cannons after the bright flash of the cannon fire. The sound would be heard an appreciable instant after the flash because light travels faster than sound. The word "thundered" suggests a comparison with the flash of lightning and the thunder which follows it.
