shavetail
/ˈʃeɪvteɪl/noun
1- US military slang, often derogatory a newly commissioned officer, especially a second lieutenant〈美军俚, 常贬〉新任军官（尤指少尉）。
1.1
- informal an inexperienced person〈非正式〉没有经验的人：
as modifier the shavetail Assistant District Attorney.缺少经验的地方检察官助理。
词源
figuratively, from the early sense 'untrained pack animal' (identified by a shaven tail).