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

noun

1. one of the cross braces that support the rails on a railway track

e.g. the British call a railroad tie a sleeper

Synonym: tiecrosstiesleeper