名詞 sideline:

1. a line that marks the side boundary of a playing field
   同義詞：out of bounds
2. an auxiliary line of merchandise
3. an auxiliary activity
   同義詞：avocation, by-line, hobby, pursuit, spare-time activity

動詞 sideline:

1. remove from the center of activity or attention; place into an inferior position

1. Actually I'm a teacher, my writing is just a sideline.
   我其實是個教師，寫作只是我的兼職。
2. I was on the sidelines during the political crisis.
   在這一政治危機(jī)時期我是目睹一切的局外人。