The speaker of the poem describes the fellow soldier who inhales poison gas as “stumbling” around, yelling, and “flound’ring” like a man on fire or as one who is “drowning” and gasps for air. He reports that he has frequent, vivid dreams in which this doomed soldier “plunges at [him], guttering, choking, drowning.” Given this description, it sounds as though the speaker has a clear memory of the poor man’s movements immediately after he has inhaled the poison that will proceed to kill him, slowly and painfully.

People are typically not described as performing the action of “guttering,” though the intransitive verb “to gutter” can refer to something that either flows or inclines downward; for example, a liquid could gutter, or flow, down a hill, or a candle flame can gutter in a draft of wind. Therefore, one can interpret this word choice of “guttering” as the man stumbling toward the speaker or even dropping to his knees in front of the speaker. The man seems to be “choking,” in all likelihood, because he is inhaling something caustic and poisonous, and so he likely would be literally choking on whatever he has inhaled. Finally, this doomed man appears to be “drowning,” though he is not literally drowning. He is, perhaps, flailing his arms and gasping for breath as a drowning man might do. In short, these three present participles are verbs and also function like adjectives, describing the behavior of the doomed soldier after he inhaled the gas that will kill him.