A generally rhombus-shaped reversible cutting insert comprising: two opposing end surfaces interconnected by a continuous peripheral surface, the peripheral side surface having alternating obtuse and acute corner surfaces (30, 32) separated by four side surfaces; a median plane located between the two opposing end surfaces and intersecting the peripheral surface, an insert axis perpendicular to the median plane and about which the cutting insert is indexable, a nose cutting edge formed at the intersection of each acute corner surface and each end surface, a longitudinal plane containing the insert axis and bisecting the four nose cutting edges, each end surface having a corner abutment surface adjacent each nose cutting edge and a rake surface located therebetween, a nose point located at an intersection of each nose cutting edge and the longitudinal plane, and each corner abutment surface located closer to the median plane than its adjacent nose point, wherein: the median plane intersects each side surface to form a side boundary line (Ls); and in a cross-sectional view of the cutting insert taken along the longitudinal plane, a first imaginary straight line containing any one of the nose points and a radially outermost point (No) of the adjacent corner abutment surface forms an acute first angle (β1) greater than 25° with the median plane; characterised in that: two side boundary lines (Ls) converge towards the same acute corner surface to form an acute nose corner angle (α1) which is less than 60°; a ramp surface is located between each rake surface and its associated corner abutment surface; and in the cross-sectional view of the cutting insert taken along the longitudinal plane, a second imaginary straight line tangential to a ramp point on the ramp surface forms an acute second angle (β2) with the median plane, and the second angle (β2) is greater than the first angle (β1). two opposing end surfaces interconnected by a continuous peripheral surface, the peripheral side surface having alternating obtuse and acute corner surfaces (30, 32) separated by four side surfaces; a median plane located between the two opposing end surfaces and intersecting the peripheral surface, an insert axis perpendicular to the median plane and about which the cutting insert is indexable, a nose cutting edge formed at the intersection of each acute corner surface and each end surface, a longitudinal plane containing the insert axis and bisecting the four nose cutting edges, each end surface having a corner abutment surface adjacent each nose cutting edge and a rake surface located therebetween, a nose point located at an intersection of each nose cutting edge and the longitudinal plane, and each corner abutment surface located closer to the median plane than its adjacent nose point, wherein: the median plane intersects each side surface to form a side boundary line (Ls); and in a cross-sectional view of the cutting insert taken along the longitudinal plane, a first imaginary straight line containing any one of the nose points and a radially outermost point (No) of the adjacent corner abutment surface forms an acute first angle (β1) greater than 25° with the median plane; characterised in that: two side boundary lines (Ls) converge towards the same acute corner surface to form an acute nose corner angle (α1) which is less than 60°; a ramp surface is located between each rake surface and its associated corner abutment surface; and in the cross-sectional view of the cutting insert taken along the longitudinal plane, a second imaginary straight line tangential to a ramp point on the ramp surface forms an acute second angle (β2) with the median plane, and the second angle (β2) is greater than the first angle (β1). the median plane intersects each side surface to form a side boundary line (Ls); and in a cross-sectional view of the cutting insert taken along the longitudinal plane, a first imaginary straight line containing any one of the nose points and a radially outermost point (No) of the adjacent corner abutment surface forms an acute first angle (β1) greater than 25° with the median plane; characterised in that: two side boundary lines (Ls) converge towards the same acute corner surface to form an acute nose corner angle (α1) which is less than 60°; a ramp surface is located between each rake surface and its associated corner abutment surface; and in the cross-sectional view of the cutting insert taken along the longitudinal plane, a second imaginary straight line tangential to a ramp point on the ramp surface forms an acute second angle (β2) with the median plane, and the second angle (β2) is greater than the first angle (β1). two side boundary lines (Ls) converge towards the same acute corner surface to form an acute nose corner angle (α1) which is less than 60°; a ramp surface is located between each rake surface and its associated corner abutment surface; and in the cross-sectional view of the cutting insert taken along the longitudinal plane, a second imaginary straight line tangential to a ramp point on the ramp surface forms an acute second angle (β2) with the median plane, and the second angle (β2) is greater than the first angle (β1).