插足

chāzú
  1. to squeeze in
  2. to step in
  3. to take part
  4. to step between (two persons in a relationship)

CEDICT

  1. (figurative) to get involved in; (especially of a third person) to step between (two persons in a love relationship)
  2. (figurative, usually derogatory) to set foot in; to put one's feet on
  3. to get involved in; (especially of a third person) to step between (two persons in a love relationship)
  4. to set foot in; to put one's feet on

Wiktionary

加入、参与。如：「我也插足其间，和他们同乐。」也作「插脚」。

重編國語辭典

Entry Composition

=1 插 chā
  1. to insert
  2. stick in
  3. pierce
  4. to take part in
  5. to interfere
  6. to interpose
=1 插 chā old variant of 插 chā
2 足 zú
  1. (bound form) foot; leg
  2. sufficient; ample
  3. as much as; fully

Related entries

迈进 màijìn
  1. to step in
  2. to stride forward
  3. to forge ahead
出面 chūmiàn
  1. to appear personally
  2. to step in
  3. to step forth
  4. to show up
直到党委书记出面加以解释，才算打消了这种想法。

Only when the Party Committee Secretary came in person to resolve it was this point of view dispelled entirely.

Source: Tatoeba

出赛 chūsài
  1. to compete
  2. to take part (in a sports event)
参加 cānjiā
  1. to participate
  2. to take part
  3. to join
參加吧！

Enlist!

Source: Tatoeba