1. 铁路枕木：secondary manufacture 二次加工 | railroad tie 铁路枕木 | means of transportation 交通工具
2. 铁道枕木：铁道 Railroad | 铁道枕木 Railroad tie | 铁道 Railway
3. 铁路轨枕：railroad through transport ==> 铁路联运 | railroad tie ==> 铁路轨枕 | railroad track ==> 铁路轨道
4. (枕木)：◆ sledge(雪橇) sled | ◆ sleeper(枕木) railroad tie | ◆ smack (掌击;掴) slap
railroad tie什么意思