Date: 202104
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground ZZZ
Second aircraft: B757 Undifferentiated or Other Model
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Situational Awareness; Time Pressure
Second reporter function: First Officer; Pilot Not Flying
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Took Evasive Action
Contributing factors: Environment - Non Weather Related; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: We pushed off of [the] gate. My First Officer (F/O) gave a courtesy push call to Ground and we were told to expect Runway XXL. After push; F/O requested taxi. A different voice than previous Controller on same frequency gave us taxi clearance. Clearance was 'Taxi Runway XXL via Hotel and Golf.' Taxiing from the non-movement area; approaching Taxiway; I announced 'clear left' and I looked as far back as I could see over my left shoulder out of the left cockpit window. As I started a slow turn onto the taxiway; I visually cleared left again and saw a (other carrier) 757 rapidly approaching so I immediately stopped and set the parking brake. The traffic passed very close to us. This entire event was witnessed by a Company aircraft; which was holding short of the taxiway. We thought he was waiting for us so he could taxi into the ramp. My First Officer double checked our taxi clearance with Ground; about two minutes after the traffic passed. He confirmed it was 'Taxi XXL via Hotel and Golf.' After we had our clearance confirmation; the holding Company aircraft mentioned on the frequency something to the effect that the 757 passed very close to us.


Second narrative: On taxi out to Runway XXL in ZZZ; our clearance was 'Taxi XXL via H; G'. Approaching H from the ramp area; we noticed an inbound Company aircraft that we needed to either yield to; or hear confirmation that he was going to yield to us prior to entering the ramp. The Crew of that aircraft saw us as well and were able to reach Ground Control before we could to clarify whether they should enter the ramp before us or after we had past. Ground Control advised them to hold position and issued us no further instructions so we were continuing with our previously assigned clearance to taxi via H; G to XXL. Approaching the taxiway the Captain cleared left and noted that Company aircraft was waiting; while I cleared Right. While making the turn onto the taxiway; the Captain did one more glance to the left and brought the aircraft to an abrupt stop. Just then I noticed a (other carrier) 757 taxiing down G that we had had no prior information on. The Captain was able to stop the aircraft and maintain separation. We held there for (other carrier) aircraft to pass by on G and then re-cleared both left and right and proceeded onto G as previously instructed. We confirmed our clearance with Ground Control to which they again verified we were to taxi XXL via H; G. No hold shorts or information concerning other aircraft were given other than the inbound Company aircraft being told to hold his position when he made the inquiry about entering the ramp in reference to us taxiing out. The (other carrier) 757 was never mentioned.


Synopsis: Air Carrier Pilot Crew reported a critical ground conflict during taxi.