Identifying “big pawn” bishops I use to trade my bishop pairs for opponent’s knight pair most of the time. But since my recent peak of interest in the game, I have been doing studying and learning. Thus, the bishop is one of my points of interest now.

I was watched this video by agadmator that demonstrated amazing gameplay by Aronian Levonm

[Title "Aronian Levobn-Vidit Santosh Gujrathi, FIDE Chess.com Online Nations Cupm 6/5/2020"]
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1. Nf3 d5 2. e3 c5 3. c4 d4 4. exd4 cxd4 5. Bd3 Nc6 6. O-O Nf6 7. Bc2 Bg4 8. Ba4 Nd7 9. h3 Bh5 10. d3 e5 11. Re1 Be7 12. Nbd2 O-O 13. Ne4 Qc7 14. a3 a5 15. Ng3 Bg6 16. Bxc6 bxc6 17. Nxd4 exd4 18. Rxe7 Qd6 19. Re2 Nc5 20. Ne4 Nxe4 21. dxe4 Rfe8 22. f3 a4 23. c5 Qxc5 24. Bf4 Qb6 25. Rc1 c5 26. Rc4 f6 27. Qc1 Ra5 28. Rec2 f5 29. Rxc5 Rxc5 30. Rxc5 fxe4 31. fxe4 d3 32. Be3 Qe6 33. Rc7 Qxe4 34. Bd2 h6 35. Qc5 Bf7 36. Bc3 Qg6 37. Re7 Rxe7 38. Qxe7 Kh7 39. Qe5 Be8 40.  Kf2 Bf7 41. g4 Bb3 42. Ke3 Bc2 43. Kd2 Bb3 44. Ke3 Bc2 45. Kd2 Bb3 46. Qe7 Bc2 47. b4 axb3 48. Bb2 h5 49. g5 h4 50. a4 Kg8 51. a5 Kh7 52. a6 Bd1 53. Kxd1 d2 54. Qxg7+ Qxg7 55. Bxg7 Kxg7 56. Kxd2


On move 48, it can be seen that Black’dsbishop is trapped, which led to blacks defeat. Would this bishop be considered a “big pawn?”

Here are my observations.

1) Almost every example of big pawn that can found, such as here are situations where a player has played in such a way that they end up with pieces called big pawn. In the Levon game, it was trapped ( basically pushing your own pieces inactive(or passive) vs forced inactive(or passive))

2) Everytime a bishop is blocked by pawn and has restricted movement, it's supposedly a big pawn

3) In the book “What It Takes To Be A Chess Master” by Andrew Soltis, which is Wikipedia source for the definition of a big pawn,its seems just like a funny comment. Like, is it even supposed to be like a Chess term!
A "big pawn" bishop is kind of an informal term. In general it can be thought of as a bad bishop with especially limited movement. In the game you posted, that bishop could be considered a big pawn - there are pawns on its same colour, and they clearly restrict its movement. 

However, whether it's technically a bad bishop is debatable, since the b3- and d3-pawns are fixed by White's pieces (not pawns). If the king or bishop moved away, perhaps these pawns would have advanced while the bishop was still on the board, allowing it to escape and not be considered bad or trapped.

To summarize, a big pawn is essentially a bishop which is both technically bad (pawns on its colour) and clearly inactive (lacking sufficient mobility on useful squares).