Valmiki Ramayana Yuddha Kanda Sarga 86 Shloka 2
Original Shlokaयदेतद्राक्षसानीकंमेघश्यामंविलोक्यते । एतदायोध्यतांशीघ्रंकपिभिपादपायुधैः ।।6.86.2।।
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मेघश्यामम् dark as cloud, यत् that which, एतत् all that, राक्षसानीकम् army of Rakshasas, विलोक्यते be engaged, एतत् all this, पादपायुधैः trees as weapons, कपिभिः monkeys too, शीघ्रम् swiftly, अयोध्यताम् will get engaged
"The army of Rakshasas looks like a dark cloud and let the monkeys too get engaged to fight swiftly with trees as weapons."