In the Duolingo courses I came across the sentence:
Please tell me the meaning of this word.
The thing is 答える is an intransitive verb (自動詞); and in other sentences things like 質問に答える are being used.
So the question about why on that particular sentences it uses を...
I am familiar with the use of を for intransitive verbs of motion.
- 学校に行く : to go to school (に marks the purpose, the goal)
- 公園を歩く: to walk in(across) the park (を marks the medium by which the walking is done)
So I suppose it is something similar:
- 質問に答える : answer to a question (に marks the purpose, the goal)
- 意味を答える : answer "with/by" a meaning (を marking the "medium" by which the answering is done: trough the meaning)
Note that that last point is just a speculation of mine.
While there are various examples of ~を答える to be found, even in dictionaries; I haven't seen so far an explanation of it (for 答える; for verbs of motion yes, a lot), and so I am not fully confident my interpretation is correct.
Advice from a native speaker of more knowledgeable would be welcome.