This is the 1338th most frequent Japanese word.
ぐち
Complaint; grumble.
ぐち in this sentence is used to mean 'complaint' or 'grievance', and 'ぐちをこぼす' means 'to complain'.
その会議の後、彼はぐちをこぼしていた。
After that meeting, he was complaining.
ぐち here refers to voicing repeated complaints, emphasizing a negative and habitual aspect.
ぐちばかり言っても何も始まらないよ。
Nothing will begin if you only complain.
ぐち is utilized to signify the complaints or grumblings from a prior discussion.