もらい者の馬の口の中をのぞくな。

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

horse; promoted bishop

mouth; opening; hole; gap; orifice; mouth (of a bottle); spout; nozzle; mouthpiece; gate; door; entrance; exit; speaking; speech; talk (i.e. gossip); taste; palate; mouth (to feed); opening (i.e. vacancy); available position; invitation; summons; kind; sort; type; opening (i.e. beginning); counter for mouthfuls, shares (of money), and swords

inside; in; among; within; center (centre); middle; during; while

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to remove; to eliminate; to eradicate; to exclude; to except

(sentence end, mainly masc.) indicates emotion or emphasis; (used with masu stem verb) command; (used with dictionary form verb) prohibition